A treatise on the origin, progress, prevention, and cure of dry rot in timber

by Thomas Allen Britton

“‘SEASONING’ BY BRIBES.”

A certain quantity of well-seasoned oak being required, Government issues tenders for the supply of the requisite amount. A number of contractors submit their tenders to a board appointed for the purpose of receiving them, who are regulated in the choice of a contractor not by the amount of his tender, but of his bribe. The fortunate individual selected immediately sub-contracts upon a somewhat similar principle. Arranging to be supplied with the timber for half the amount of his tender, the sub-contractor carries on the game, and perhaps the eighth link in this contracting chain is the man who, for an absurdly low figure, undertakes to produce the seasoned wood.

His agents in the central provinces accordingly float a quantity of green pines and firs down the Dnieper and Bog to Nicholaeff, which are duly handed up to the head contractor, each man pocketing the difference between his contract and that of his neighbour. When the wood is produced before the board appointed to inspect it, another bribe seasons it; and the Government, after paying the price of well-seasoned oak, is surprised that the 120-gun ship, which it has been built of it, is unfit for service in five years.

“Mark but my fall, and that that ruin’d me,

Corruption.”—Shakspeare.

A few words can only be given to a most important matter, viz., the second seasoning, which many woods require. If floor-boards are only laid down at first on the joists of a building, and at the expiration of one year wedged tight and nailed down, those unsightly openings caused by shrinkage, which form a harbour for dirt and vermin, will be avoided, as the wood will have had an opportunity of shrinking. Doors, sashes, architraves in long lengths, will also be better if made up some time before they are required for use. Many Indian woods require a second seasoning—kara mardá, for instance, a favourite wood with Indian railway engineers. Even sál and teak are not exempt. Teak shrinks sideways least of all woods. In the ‘Tortoise,’ store ship, when fifty years old, no openings were found to exist between the boards; yet Colonel Lloyd says he found the teak timbers used by him in constructing a large room in the Mauritius to have shrunk ¾ of an inch in 38 feet. Thus a space of ⅜ of an inch must have been left at each end of the beam, where moisture could lodge and fungi exist, obtaining their nourishment from the wood. If unseasoned teak is used for ships, dry rot will in time find a place. It may be said that teak is a very hard wood, and very durable; yet “the mills of the gods,” says an ancient philosopher, “grind slow, very slow, but they grind to powder;” and so do the fungi mills.

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CHAPTER V.
ON SEASONING TIMBER BY PATENT PROCESSES, ETC.

Long years of practical experience has shown that timber, however prone to dry or wet rot, may be preserved from both by the use of certain metallic solutions, or other suitable protective matters.

All the various processes may be said somewhat to reduce the transverse strength of the timber when dry, and the metallic salts are affected at the iron bolts or fastenings. The natural juices of some woods do this; and bolts which have united beams of elm and pitch pine will often corrode entirely away at the junction.

The processes adopted for resisting the chemical changes in the tissues of the wood are all founded on the principle that it is essential to inject some material which shall at once precipitate the coaguable portion of the albumen retained in the tissues of the wood in a permanent insoluble form, so that it will not hereafter be susceptible of putrefactive decomposition. For this purpose, many substances, many solutions, have been employed with variable success, but materials have been sometimes introduced for this purpose which produced an effect just the opposite to what was anticipated.

Experience has shown that timber is permeable, at least by aqueous solutions, only so long as the sap channels are free from incrustation.

Such in general is the case with beech, elm, poplar, and hornbeam, the capillary tubes of which are always open, or, at least, close very slowly. At the same time it may be said that there must remain ever in these species some parts impervious to injection, whilst it is almost impossible but that a certain portion of the fibres will be more or less incrusted. The sap woods, on the other hand, of every species appear quite pervious.

Very little is known of any preservative process adopted in ancient times. Pliny observes that the ancients used garlic boiled in vinegar with considerable success, especially with reference to preserving timber from worms: he also states that the oil of cedar will protect any timber anointed with it from worm and rottenness. Oil of cedar was used by the ancient Egyptians for preserving their mummies. Tar and linseed oil were also recommended by him. The image of the goddess Diana, at Ephesus, was saturated with olive and cedar oils; also the image of Jupiter, at Rome; and the statues of Minerva and Bacchus were impregnated with oil of spikenard.

The idea of preserving wood by the action of oil is therefore by no means new; but it is somewhat curious that the earliest modern processes should also be by means of oil. The oils most proper to be used are linseed, rapeseed, or almost any of the vegetable fixed oils. Oak wood, rendered entirely free from moisture, and then immersed in linseed oil, is said to be thus prevented from splitting: the time of immersion depending on the size, &c. Palm oil is preferable to whale oil, because impregnation with the latter, although in many instances eligible, causes wood to become brittle. It is, however, probable that whale oil, when combined with other substances, such as litharge, coal pitch, or charcoal, may lose much of that effect. As cocoa-nut oil, which is, under low temperature, like the oil expressed from the nuts of the palm tree, is known to be highly preservative of timber and metallic fastenings, we may expect the same result from the latter, and thereby avoid that extreme dryness and brittleness of the timber which Mr. Strange complained of in the Venetian ships that had been seasoned for many years in frame under cover. Cocoa-nut oil beat up with shell lime or chunam, so as to become putty, and afterwards diluted with more oil, is used at Bombay and elsewhere as a preservative coat or varnish to plank. It cannot become a varnish without the addition of some essential oil; and the oil of mustard is used; which, of course, will produce the desired effect. In the first volume of the Abbé Raynal, on the European settlements in the East and West Indies, he mentions that an oil was exported from Pegu for the preservation of ships; but as he does not say what oil, no conclusion can be drawn further than as to the probability of its being one of those already noticed.

Experience has proved that even animal oils are so far injurious to timber as to render it brittle, whilst they preserve it from rottenness; and that, on the other hand, a mineral salt more or less combined with fatty substances does not produce that effect. The staves of whale-oil casks become quite brittle, whilst those of beef, pork, and tallow barrels remain tough and sound. Ships constantly in the Greenland trade have their timbers and planks preserved so far as they have become impregnated with whale oil.

Experiments with fish oil prove that of itself, unless exposed to sun and air, it may be injurious; that it loosens the cohesion of timber; but that animal fat, combined with saline matter, is preservative.

Fish oil used alone is ineligible, because capable of running into the putrefactive process, unless as a thin outside varnish. In hard, sound timber, it will hardly enter at all; and if poured into bore-holes in the heads of timbers, it will insinuate itself into the smallest rents or cracks, and waste through them. Used alone, or with any admixture, it is absorbed and dried quickly on wood in a decomposing state or commencing to be dry rotten. Used with litharge, it dries after some days; but with lamp-black it has scarcely so much tendency to dry as when used alone. Paint of fish oil and charcoal dries very quickly where there is absorption, and the charcoal extends its oxidating or drying effect to the fish oil in its vicinity.

We give the following to prove what we have written, and also to serve as an example for those who wish to try experiments:—

EXPERIMENTS ON FISH OIL.

June 9.—Upon a piece of old oak scantling, with its alburnam on one side in a state of decay, fish oil was poured several times, viz. on this day, on June 25, and July 3, which it rapidly absorbed in the decayed part.

July 26.—It was payed (or mopped) with fish oil and charcoal powder, and the following day it was put under an inverted cask.

October 1.—The end of this piece was covered with a greenish mould. This proves that fish oil must be injurious, except where exposed to sun and air to dry it.

A compound of fixed oils and charcoal is liable to inflame, but as a thin covering or pigment it may not be so.

The petroleum oil-wells, near Prome, in Burmah, have been in use from time immemorial. Wood, both for ship-building and house-building, is invariably saturated or coated with the product of those wells; and it is stated that the result is entire immunity from decay and the ravages of the white ant. At Marseilles, and some other ports in the Mediterranean, it used to be the practice to run the petroleum, which is obtained near the banks of the Rhone, into the vacancies between the timbers of the vessels, to give them durability. It was sometimes, for the conjoint purpose of giving stability and duration to vessels, mixed with coarse sand or other extraneous matters, and run in whilst hot between the ceiling and bottom plank, where it filled up the vacancies between the timbers in the round of their bottoms, excepting where necessary to be prevented. The great objection to the use of petroleum is its inflammability. Creosote, its great rival for wood preserving, is also inflammable, and not so agreeable in colour; but it is considerably cheaper, which is an important matter.

As we are now about to enter upon the subject of patent processes, &c., it appears desirable to lay down certain principles at the commencement, in order to assist the reader as much as possible.

Almost every chemical principle or compound of any plausibility has been suggested in the course of the last hundred and fifty years; but the multiplicity and contradiction of opinions form nearly an inextricable labyrinth. To commence.

1st. It seems obvious that the sooner the sap is wholly removed from the wood the better, provided the woody fibre solidifies without injury.

2nd. That the wood should be impregnated with any strongly antiseptic and non-deliquescent matter, which must necessarily be in solution when it enters the wood. No deliquescent remedy is eligible, because moisture is injurious to metallic fastenings.

3rd. The wood should be first dried, and its pores then closed with any substance impervious to air and moisture, and at the same time highly repellant to putrescency. The most essential requisites in a preservative of timber being a disposition to dryness, and a tendency to resist combustion as far as consistently obtainable.

4th. Any process to be successful ought not to be tedious, very difficult, or too expensive. These are important elements in the success of any patent.

Very little is known of any preservative process previous to the year 1717, when directions were given by the Navy authorities to boil treenails, and dry them before they were used. But whether the custom had prevailed before this time, or whether their strength and durability were increased by it, there are no means of ascertaining. It does not appear that any substance was put into the water to decompose the juices; but as they are soluble in warm water, perhaps the power of vegetation might have been destroyed without it.

In 1737 Mr. Emerson patented a process of saturating timber with boiled oil, mixed with poisonous substances; but his process was very little used. This, we believe, was the first patent on wood preserving.

About 1740, Mr. Reid proposed to arrest decay by means of a certain vegetable acid (probably pyroligneous acid). The method of using it was by simple immersion.

In 1756, Dr. Hales recommended that the planks at the water-line of ships should be soaked in linseed oil, to prevent the injury to which wood is subject when alternately exposed to wet and dry; and indeed, many ships were built in which a hollow place was cut in one end of each beam or sternpost, which might constantly be kept filled with train oil. Amongst other ships so constructed, the ‘Fame,’ 74, may be mentioned. When, after some years, this ship was repaired, it was found that as far as the oil had penetrated, namely, from 12 to 18 inches from the end, the wood was quite sound, whilst the other parts were more or less decayed. The Americans used to hollow out the tops of their masts in the form of cups or basins; bore holes from the end a considerable way down the masts; pour oil into these; cover them over with lead; and leave the oil to find its way down the capillary vessels to the interior of the timber.[7]

In 1769, Mr. Jackson, a London chemist, with a view to the prevention of decay, obtained permission to prepare some timber to be used in the national yards, by immersing it in a solution of salt water, lime, muriate of soda, potash, salts, &c., the result of which dose was, that several frigates in the Navy subjected to the process were rendered more perishable than if they had been constructed of unprepared timber. The solution was filtered into the wood partly by means of holes made in it. Chapman proposed a similar method of preserving the frames of ships, viz. by boring holes in the timbers, and pumping a solution of copperas in water into them. He believed every part of the vessel would thus be impregnated.

Mr. Jackson also prepared the frame of the ship ‘Intrepid’ with another solution. The ship lasted many years. Bowden thought it was a solution of glue. Chapman suggested slaked lime, thinned with a weak solution of glue for mopping the timbers of a ship.

Shortly after Mr. Jackson’s process was started, Mr. Lewis attempted to accomplish the preservation of timber by placing it surrounded by pounded lime, in spaces below the “surface of the earth.” The use of lime has also been advocated by Mr. Knowles, Secretary of the Committee of Surveyors of the Navy, who has written an able work on the ‘Means to be taken to Preserve the British Navy from Dry Rot’ (1821).

Between 1768 and 1773 a practice prevailed of saturating ships with common salt; but this was found to cause a rapid corrosion of the iron fastenings, and to fill the vessels between decks with a constant damp vapour. In ‘Nicholson’s Journal,’ No. 30, there is an article signed Nauticus on this subject. Vessel owners had long ago observed that those ships which have early sailed with cargoes of salt are not attacked by dry rot. Indeed, several instances are attested of vessels whose interiors were lined with fungi having all traces of the plant destroyed by accidental or intentional sinking in the sea. Acting on such hints, a trader of Boston, U. S., salted his ships with 500 bushels of the chloride, disposed as an interior lining, adding 100 bushels at the end of two years. Such an addition of dead weight is sufficient objection to a procedure which has other great disadvantages. Salt should never be applied as an antidote against the dry rot, on account of its natural powers of attracting moisture from the atmosphere, which would render apartments almost uninhabitable, from their continual dampness. Those who have lived for any length of time in a house at the sea-side, the mortar of which has been partly composed of sea sand, will have observed the moist state of the paper, plastering, &c., in wet weather. Bricks made with sea sand are objectionable.

Salt water seasoning has already been referred to in the last chapter, but as it is so closely connected with salt seasoning, the further and final consideration of salt water seasoning may be fitly dealt with here. Salt water will not extract the juices from the timber like fresh water. It is only by destroying the vegetation that salt water can be advantageous, but it would require a very long time to impregnate large timber to the heart so as to destroy vegetation. It is well known that wood is softened, and in time decomposed, by extreme moisture. Fifty years since, the master builder at Cronstadt complained that the oak from Casan, which was frequently wet from different causes in its passage of three years to Cronstadt, was so water-soaked as never to dry; and also from the information of Mr. Strange, it appears “that the practice at Venice of the fresh-cut timber being thrown into salt water, prevents its ever becoming dry in the ships, and that the salt water rusted and corroded the iron bolts.” In fine, vessels built with salt water seasoned wood are perfect hygrometers, being as sensible to the changes of the moisture of the atmosphere as lumps of rock salt, or the plaster of inside walls where sea sand has been used.

In Ceylon, the timber of the female palm tree is much harder and blacker than that of the male, inasmuch as it brings nearly triple its price. The natives are so well aware of the difference that they resort to the devise of immersing the male tree in salt water to deepen its colour, as well as add to its weight.

Vessels impregnated with bay salt, or the large grained salt of Leamington or of Liverpool (pure muriate of soda), will possess decided advantages; as also will vessels that have been laden with saltpetre, if it has been dispersed amongst their timbers.

Ships (the timbers of which had been previously immersed in salt water) have been broken up after a few years’ service, and the floor timbers taken out quite sound: but when exposed to the sun and rain in the summer months, their albumen has been in a decomposed or friable state.

By the answers to queries given to Mr. Strange, the British Minister at Venice, in or about 1792, it appears that several of the Venetian ships of war had then lain under sheds for fifty-nine years; some in bare frames, and others planked and caulked: that these ships show no outward marks of decay; but their timbers have shrunk much, and become brittle; that some of the most intelligent ship builders were of opinion that great prejudice had arisen from the prevalent custom of throwing the timber fresh cut into salt water, and letting it lie there until wanted; that afterwards it dried, and withered on the outside, under the sheds, while the inside, being soaked with salt water, rotted before it became dry; and this was one reason, amongst others, why Venetian ships, though built of good timber, lasted so short a time; for the salt moisture not only rots the inside of the beams and timbers, but of course rusts and corrodes the iron bolts.

Salt water, sea-sand, and sea-weed are now used for seasoning “jarrah” wood in Western Australia. This wood is considered a first-class wood for ship-building, but it is somewhat slow to season, and if exposed before being seasoned it is apt to “fly” and cast. The method adopted is as follows: The logs are thrown into the sea, and left there for a few weeks; they are then drawn up through the sand, and after being covered with sea-weed a few inches deep, are left to lie on the beach, care being taken to prevent the sun getting at their ends. The logs are then left for many months to season. When taken up they are cut into boards 7 inches wide, and stacked, so as to admit of a free circulation of air round them, for five or six months before using them. Sea-weed or sea-ware, cast upon the shores, contains a small quantity of carbonate of soda, and a large proportion of nitrogenous and saline matters, with earthy salts, in a readily decomposable state. They also contain much soluble mucilage. The practice of seasoning timber by heating it in a sand bath was formerly adopted by the Dutch, and by the Russians in building boats. Mr. Thomas Nichols (in a letter to Lord Chatham, when First Lord of the Admiralty) states “that the same end, viz. preservation of timber from decay, might probably be acquired by burying the timber in sand, which acts as an artificial sap,” in the same manner as mentioned in Townsend’s ‘Travels through Spain,’ to be used with the masts of ships of war at Cadiz.

Peat moss has been recommended (because the sulphates of iron, soda, and magnesia are found in it), but it failed when tried.

With reference to Mr. Lewis’s proposal to preserve wood by means of lime, it must be remembered that quicklime, with damp, has been found to accelerate putrefaction, in consequence of its extracting carbon; but when dry, and in such large quantities as to absorb all moisture from the wood, the wood is preserved, and the sap hardened. Vessels long in the lime trade have afforded proof of this fact; and we have also examples in plastering-laths, which are generally found sound and good in places where they have been dry. Whitewash or limewater has been strongly recommended for use between the decks of ships, as being unfavourable to vegetation: it should be renewed at intervals of time, according to circumstances. It has been applied with good effect to the joists and sleepers of kitchen floors; but to be effectual it should be occasionally renewed. Effete, or re-carbonated lime, is injurious to timber, like other absorbent earths; so also are calcareous incrustations formed by the solution of lime in water, as appears from Von Buch’s ‘Travels in Norway,’ in which he says, “that in the fishing country (near Lofodden, beyond the Arctic circle) the calcareous incrustations brought by water, filtering through a bed of shells, soon cause the vessels and wood to be covered with and destroyed by green fungi.” The ends of joists of timber inserted in walls are frequently found rotten; and where not so, it may probably be owing to the mortar having been made with hot lime, and used immediately, or to the absence of moisture. It does not appear practicable to use limewater to any extent for preserving timber, because water holds in solution only about ⅟500th part of lime, which quantity would be too inconsiderable; it, however, renders timber more durable, but at the same time very hard and difficult to be worked (p. 73).

Vessels constantly in the coal trade have generally required little repair, and have lasted until in the common course of things they were lost by shipwreck. This must be owing to the martial pyrites which abound in all coals; and also from the sulphuric acid arising from the quantity of coal dust which finds its way through the seams of the ceiling, and adheres to the timber and planks.

In 1779, M. Pallas, in Russia, proposed to steep wood in sulphate of iron (green vitriol) until it had penetrated deeply, and then in lime to precipitate the vitriol. Neumann, in his first volume of ‘Chemistry,’ on the article green vitriol, says, “That in the Swedish transactions this salt is recommended for preserving wood, particularly the wheels of carriages, from decay.

“When all the pieces are fit for being joined together, they are directed to be boiled in a solution of vitriol for three or four hours, and then kept for some days in a warm place to dry. It is said that the wood by this preparation becomes so hard and compact that moisture cannot penetrate it, and that iron nails are not so apt to be destroyed in this vitriolated wood as might be expected, but last as long as the wood itself.”

In 1780 the marcasite termed by the miners mundic, found in great abundance in the tin mines in Devonshire and Cornwall, was employed, in a state of fusion, to eradicate present and to prevent the future growth of dry rot; but whether its efficacy was proved by time is not known. A garden walk where there are some pieces of mundic never has any weeds growing; the rain that falls becomes impregnated with its qualities, and in flowing through the walk prevents vegetation.

In 1796 Hales proposed to creosote the treenails of ships: this was forty-two years previous to Bethell’s patent for creosoting wood.

About the year 1800, the Society of Arts’ building in the Adelphi, London, being attacked by dry rot, Dr. Higgins examined the timbers, caused some to be removed and replaced by new, and the remainder to be scraped and washed with a solution of caustic ammonia, so as by burning the surface of the wood to prevent the growth of fungi.

At the commencement of the present century, a member of the Royal Academy of Stockholm called attention to the use of alum for preserving wood from fire. He says, in the Memoirs of that Academy, “Having been within these few years to visit the alum mines of Loswers, in the province of Calmar, I took notice of some attempts made to burn the old staves of tubs and pails that had been used for the alum works. For this purpose they were thrown into the furnace, but those pieces of wood which had been penetrated by the alum did not burn, though they remained for a long time in the fire, where they only became red; however, at last they were consumed by the intenseness of the heat, but they yielded no flame.” He concludes, from this experiment, that wood or timber for the purpose of building may be secured against the action of fire by letting it remain for some time in water wherein vitriol, alum, or any other salt has been dissolved which contains no inflammable parts.

In Sir John Pringle’s Tables of the antiseptic powers of different substances, he states alum to be thirty times stronger than sea-salt; and by the experiments of the author of the ‘Essai pour servir à l’Histoire de la Putréfaction,’ metallic salts are much more antiseptic than those with earthy bases.

In 1815 it occurred to Mr. Wade that it would be a good practice to fill the pores of timber with alumine, or selenite; but two years after, Chapman observed, “Impregnation of ships’ timbers with a solution of alum occurred to me about twenty years since, because on immersion in sea-water the alumine would be deposited in the pores of the timber; but I was soon informed of its worse than inutility, by learning that the experiment had been tried, and, in place of preserving, had caused the wood to rot speedily. Impregnation with selenite has been tried in elm water-pipes. On precipitation from its solvent it partially filled the pores, and hardened the wood, but occasioned speedy rottenness.” If, by using a solution of alum to render wood uninflammable, we at the same time cause it to rot speedily, it becomes a question whether the remedy is not worse than the disease. Captain E. M. Shaw, of the London Fire Brigade, in his work, ‘Fire Surveys’ (1872), recommends alum and water. Probably he only thought of fire, and not of rotting the wood. The alum question does not appear to be yet satisfactorily settled.

While upon the subject of uninflammable wood, we may state that in 1848, upon Putney Heath (near London), by the roadside, stood an obelisk, to record the success of a discovery made in the last century of the means of building a house which no ordinary application of ignited combustibles could be made to consume: the obelisk was erected in 1786. The inventor was Mr. David Hartley, to whom the House of Commons voted 2500l., to defray the expenses of the experimental building, which stood about one hundred yards from the obelisk. The building was three stories high, and two rooms on a floor. In 1774, King George the Third and Queen Charlotte took their breakfast in one of the rooms, while in the apartment beneath fires were lighted on the floor, and various inflammable materials were ignited to attest that the rooms above were fire-proof. Hartley’s secret lay in the floors being double, and there being interposed between the two boards sheets of laminated iron and copper, not thicker than stout paper, which rendered the floor air-tight and thereby intercepted the ascent of the heated air; so that, although the inferior boards were actually charred, the metal prevented the combustion taking place in the upper flooring. Six experiments were made by Mr. Hartley in this house in 1776, but we cannot ascertain any particulars about them, or any advantages which accrued to the public from the invention, although the Court of Common Council awarded him the freedom of the City of London for his successful experiments.

In 1805 Mr. Maconochie proposed to saturate with resinous and oily matters inferior woods, and thus render them more lasting. This proposal was practically carried out in 1811 by Mr. Lukin, who constructed a peculiar stove for the purpose of thus impregnating wood under the influence of an increased temperature. The scheme, however, had but very partial success, for either the heat was too low and the wood was not thoroughly aired and seasoned, or it was too high and the wood was more or less scorched and burnt. Mr. Lukin buried wood in pulverized charcoal in a heated oven, but the fibres were afterwards discovered to have started from each other. He next erected a large kiln in Woolwich dockyard, capable of containing 250 loads of timber, but an explosion took place on the first trial, before the process was complete, which proved fatal to six of the workmen, and wounded fourteen, two of whom shortly afterwards died. The explosion was like the shock of an earthquake. It demolished the wall of the dockyard, part of which was thrown to the distance of 250 feet; an iron door weighing 280 lb. was driven to the distance of 230 feet; and other parts of the building were borne in the air upwards of 300 feet. The experiment was not repeated.

Mr. Lukin was not so fortunate in 1811 as in 1808, for in the latter year he received a considerable reward from the Government for what was considered a successful principle of ventilating hospital ships.

In 1815 Mr. Wade recommended the impregnation of timber with resinous or oleaginous matter (preferring linseed oil to whale oil) or with common resin dissolved in a lixivium of caustic alkali, and that the timber should afterwards be plunged into water acidulated with any cheap acid, or with alum in solution. He considered that timber impregnated with oil would not be disagreeable to rats, worms, cockroaches, &c., and that the contrary was the case with resin. He also recommended the impregnation of timber with sulphate of copper, zinc, or iron, rejecting deliquescent salts, as they corrode metals.

In 1815 Mr. Ambrose Boydon, of the Navy Office, strongly recommended that the timber, planks, and treenails of ships should be first boiled in limewater to correct the acid, and that they afterwards should be boiled in a thin solution of glue, by which means the pores of the wood would be filled with a hard substance insoluble by water, which would not only give the timbers durability, by preventing vegetation, but increase their strength. Glue, he thought, might be used without limewater, or glue and limewater mixed together.

In 1817 Mr. William Chapman published the result of various experiments he had made on wood with lime, soap, and alkaline and mineral salts. He recommended a solution of a pound of sulphate of copper or blue vitriol (at that time 7d. per pound) dissolved in four ale gallons of rain water, and mopped on hot over all the infected parts, or thrown over them in a plentiful libation. He also recommended one ounce of corrosive sublimate (then 6s. per pound) to a gallon of rainwater applied in the same manner to the infected parts. For weather-boarded buildings he considered one or more coats of thin coal tar, combined with a small portion of palm oil, for the purpose of preventing their tendency to rend, to be a good preservative.

Messrs. Wade, Boydon, and Chapman published works on dry rot about this time.

In 1822 Mr. Oxford took out a patent for an improved method of preventing “decay of timber,” &c. The process proposed was as follows: “The essential oil of tar was first extracted by distillation, and at the same time saturated with chlorine gas. Proportions of oxide of lead, carbonate of lime, and carbon of purified coal tar well ground, were mixed with the oil, and the composition was then applied in thick coatings to the substances intended to be preserved.”

On 31st March, 1832, Mr. Kyan patented his process of corrosive sublimate (solution of the bi-chloride of mercury) for preventing dry rot; which process consisted as follows: A solution of the corrosive sublimate is first made, and the timber is placed in the tank. The wood is held down in such a way, that when immersed on the fluid being pumped in, it cannot rise, but is kept under the surface, there being beams to retain it in its place. There it is left for a week, after which the liquor is pumped off, and the wood is removed. This being done, the timber is dried, and said to be prepared. Sir Robert Smirke was one of the first to use timber prepared by Kyan, in some buildings in the Temple, London; and he made some experiments on timber which had undergone Kyan’s process. He says, “I took a certain number of pieces of wood cut from the same log of yellow pine, from poplar, and from the common Scotch fir; these pieces I placed first in a cesspool, into which the waters of the common sewers discharged themselves; they remained there six months; they were then removed from thence, and placed in a hotbed of compost under a garden-frame; they remained there a second six months; they were afterwards put into a flower border, placed half out of the ground, and I gave my gardener directions to water them whenever he watered the flowers; they remained there a similar period of six months. I put them afterwards into a cellar where there was some dampness, and the air completely excluded; they remained there a fourth period of six months, and were afterwards put into a very wet cellar. Those pieces of wood which underwent Kyan’s process are in the same state as when I first had them, and all the others to which the process had not been applied are more or less rotten, and the poplar is wholly destroyed.

“I applied Kyan’s process to yellow Canadian pine about three years ago, and exposed that wood to the severest tests I could apply, and it remains uninjured, when any other timber (oak or Baltic wood) would certainly have decayed if exposed to the same trial, and not prepared in that manner.

“As another example of the effect of the process, I may mention that about two years ago, in a basement story of some chambers in the Temple, London, the wood flooring and the wood lining of the walls were entirely decayed from the dampness of the ground and walls, and to repair it under such circumstances was useless. As I found it extremely difficult to prevent the dampness, I recommended lining the walls and the floor with this prepared wood, which was done; and about six weeks ago I took down part of it to examine whether any of the wood was injured, but it was found in as good a state as when first put up. I did not find the nails more liable to rust.’

“I have used Kyan’s process in a very considerable quantity of paling nearly three years ago; that paling is now in quite as good a state as it was, though it is partly in the ground. It is yellow pine. Some that I put up the year before, without using Kyan’s process (yellow pine), not fixed in the ground, but close upon it, is decayed.”

This evidence, by such an experienced architect as the late Sir Robert Smirke was, is certainly of great value in favour of Kyan’s process.

The recorded evidence upon the efficiency of this mode of treating timber for its preservation is somewhat contradictory. On the Great Western Railway 40,000 loads were prepared, at an expenditure of 1¾ lb. of sublimate to each load, the timber, 7 inch, being immersed for a period of eight days, and the uniformity of the strength of the solution being constantly maintained by pumping. Some samples of this timber, after six years’ use as sleepers on the railway, were found “as sound as on the day on which they were first put down.” This timber was prepared by simple immersion only, without exhaustion or pressure. Some of the sleepers on the London and Birmingham Railway, on the other hand, which had been Kyanized three years only, were found absolutely rotten, and Kyan’s process was there consequently abandoned.

This process is said to cost an additional expense to the owner of from fifteen to twenty shillings per load of timber. Mr. Kyan at first used 1 lb. of the salt in 4 gallons of water, but it was found that the wood absorbed 4 or 5 lb. of this salt per load; more water was added to lessen the expense, until the solution became so weak as in a great measure to lose its effect.

Simple immersion being found imperfect as a means of injecting the sublimate, attempts were afterwards made to improve the efficiency of the solution by forcing it into the wood. Closed tanks were substituted for the open ones, and forcing pumps, &c., were added to the apparatus. The pressure applied equalled 100 lb. on the square inch. With this arrangement a solution was made use of having 1 lb. of the sublimate to 2 gallons of water; and it was found that three-fourths of this quantity sufficed for preparing one load of timber. The timber was afterwards tested, and it was ascertained that the solution had penetrated to the heart of the logs. Mr. Thompson, the Secretary to Kyan’s Company, stated, in March, 1842, that experience had proved “that the strength of the mixture should not be less than 1 lb. of sublimate to 15 gallons of water; and he had never found any well-authenticated instance of timber decaying when it had been properly prepared at that strength.” As much as 1 in 9 was not unfrequently used. Kyan’s process is now but very rarely used; Messrs. Bethell, of King William Street, London, adopt it when requested by their customers. We have given the statements which have been made for and against this patent, but after a lapse of forty years it is difficult to reconcile conflicting statements.

PATENT PRESERVATIVE SYSTEM.

Horizontal Section of Mr. Kyan’s Original Tank and Cistern.

A. Bottom of Tank.

B. ¾″ Iron bolts to connect the planks which form the sides and end of the Tank and Cistern.

C. The Cistern which contains the solution.

D. The Tank.

E. Pump for raising the solution from tank into Cistern.

F. Tap for conveying the solution from Cistern to Tank.

G. Wood sleepers to carry Tank and Cistern.

Although Mr. Kyan invented his process in 1832, Sir Humphrey Davy had previously used and recommended to the Admiralty, and Navy Board, a weak solution of the same thing to be used as a wash where rot made its appearance: on giving his opinion upon Mr. Lukin’s process, that eminent chemist observed, “that he had found corrosive sublimate highly antiseptic, and preservative of animal and vegetable substances, and therefore recommended rubbing the surface of timber with a solution of it.” In 1821 Mr. Knowles, of the Navy Office, referred to the use of corrosive sublimate for timber. In fact, it was used in 1705, in Provence (France), for preserving wood from beetles. Kyan, however, was the first to apply it to any extent. In the years 1833 to 1836, at the Arsenal, Woolwich, experiments were instituted, having for their object the establishing, or otherwise, the claims of Kyan’s system; the results of which were of a satisfactory nature. Dr. Faraday has stated that the combination of the materials used was not simply mechanical but chemical; and Captain Alderson, C.E., having experimented upon some specimens of ash and Christiana deal, found that the rigidity of the timber was enhanced, but its strength was in some measure impaired; its specific gravity being also in some degree diminished.[8] Kyan’s process is said by some to render the wood brittle.

Mr. Kyan considered that the commencement of rot might be stopped or prevented by the application of corrosive sublimate, in consequence of the chemical combination which takes place between the corrosive sublimate and those albuminous particles which Berzelius and others of the highest authority consider to exist in and form the essence of wood; which, being the first parts to run to decay, cause others to decay with them. By seasoning timber in the ordinary way, the destructive principle is dried, and under common circumstances rendered inert. But when the timber is afterwards exposed to great moisture, &c. (the fermentative principle being soluble when merely dried), it will sometimes be again called into action. Kyan’s process is said not only altogether to destroy this principle and render it inert, but, by making it solid and perfectly insoluble, to remove it from the action of moisture altogether. It thus loses its hygrometric properties, and, therefore, prepared or patent seasoned timber is not liable to those changes of atmosphere which affect that which is seasoned in the common way. All woods, including mahogany and the finest and most expensive wood, may be seasoned by Kyan’s process in a very short space of time, instead of the months required by the ordinary methods.

The reader will find a great deal about Kyan’s system in the ‘Quarterly Review,’ April, 1833; and about proposals for using chloride of mercury for wood, ‘Memoirs of the Academy of Dijon,’ 1767; ‘Bull. des Sciences teen.,’ v. ii., 1824, Paris; and ‘Bull. de Pharm.,’ v. 6, 1814, Paris.

It is well known that Canadian timber is much more liable to decay than that grown in the northern parts of Europe, and for this reason is never extensively used in buildings of a superior description. The principle of decay being destroyed by Kyan’s process as above described, this objection no longer exists, and this kind of timber may therefore now be employed with as great security as that of a superior quality and higher price. The same observation applies with great force to timber of British growth, particularly to that of Scotland, much of which is considered as of little or no value for durable purposes, on account of its extreme liability to decay, whether in exposed situations or otherwise. The process invented by Kyan might therefore render of considerable value plantations of larch, firs of all kinds, birch, elm, beech, ash, poplar, &c.

Cost of process in 1832, 1l. per load of 50 cubic feet of timber.

Mr. W. Inwood, the architect of St. Pancras Church, London, reported favourably of Kyan’s process. On 22nd February, 1833, Professor Faraday delivered a lecture at the Royal Institution, London, on Kyanizing timber; and on 17th April, 1837, he reported that Kyan’s process had not caused any rusting or oxidation of the iron in the ship ‘Samuel Enderby,’ after the ship had been subjected to this process, and had been on a three years’ voyage to the South Sea fisheries; and in the same year, viz. 1837, Dr. Dickson delivered a lecture at the Royal Institute of British Architects on dry rot, recommending Kyan’s process.

Five years after Mr. Kyan’s invention, viz. in 1837, a Mr. Flocton invented a process for preventing decay, by saturating timber with wood-tar and acetate of iron, but little is known of this invention: we believe it was a failure.

During the same year Mr. Flocton’s process was made known, a Frenchman named Letellier recommended saturating timber in a solution of corrosive sublimate, and when dry, into one of glue, size, &c.[9]

During this year Mr. Margary took out his patent for applying sulphate of copper to wood. We propose to describe Margary’s process further on: we do not think he received any medals for it.

We now arrive at the modern creosoting process, which was brought to perfection by the late Mr. John Bethell. Mr. Bethell’s process of creosoting, or the injection of the heavy oil of tar, was first patented by him on July 11th, 1838.[10] It consists in impregnating the wood throughout with oil of tar, and other bituminous matters containing creosote, and also with pyrolignite of iron, which holds more creosote in solution than any other watery menstruum. Creosote, now so extensively used in preserving wood, is obtained from coal tar, which, when submitted to distillation, is found to consist of pitch, essential oil (creosote), naphtha, ammonia, &c. In the application of the oil of tar for this purpose, it is now considered to be indispensable that the ammonia be got rid of; otherwise the wood sometimes becomes brown and decays, as may be constantly seen in wood coated with the common oil tar. The kind of creosote preferred by continental engineers and chemists, and also by the late Mr. John Bethell himself, is thick, and rich in naphthaline. Some English chemists now seem to prefer the thinnest oil, which contains no naphthaline, but a little more carbolic acid; the crude carbolic acid would vary from 5 to 15 per cent.: no engineer has ever required more than 5 per cent. of crude carbolic acid in creosote. The thinner oil appears to be more likely to be drawn out of the wood by the heat of the sun or absorption in powdery soil, and is more readily dissolved out by moisture.

Mummies many thousands of years old have evidently been preserved on the creosoting principle, and from observing the mummies the process of creosoting suggested itself to Mr. Bethell. The ancient Egyptians, whether from the peculiarity of their religious opinions, or from the desire to shun destruction and gain perpetuity even for their dead bodies, prepared the corpses of their deceased friends in a particular way, viz. by coagulating the albumen of the various fluids of the body by means of creosote, cedar oil, salt, and other substances, and also by excluding the air. How perfectly this method has preserved them the occasional opening of a mummy permits us to see. A good account of the operation is given in the chapter on mummies, in the second volume of Egyptian Antiquities in the ‘Library of Entertaining Knowledge.’

By the process of creosoting the timber is rendered more durable, and less liable to the attack of worms; but it becomes very inflammable; that is, when once alight burns quickly; in addition to which, the disagreeable odour from timber so treated renders it objectionable for being used in the building of dwelling-houses.

The action of the solutions in water of metallic salts is, if the mixture is sufficiently strong, to coagulate the albumen in the sap; but the fibre is left unprotected.

Creosote has the same effect of coagulating the albumen, whilst it fills the pores of the wood with a bituminous asphaltic substance, which gives a waterproof covering to the fibre, prevents the absorption of water, and is obnoxious to animal life.

In cases where the complete preservation of timber is of vital importance, and expense not a consideration, the wood should be first subjected to Burnett’s process, and then creosoted; by which means it would be nearly indestructible; the reason for this combined process being, that the albumen or sap absorbs the creosote more readily than the heart of the timber, which can, however, be penetrated by the solution of chloride of zinc. Mr. John Bethell’s patent of 1853 recommends this in a rather improved form. He says the timber should first be injected with metallic salts, then dried in a drying-house, then creosoted. By this method, very considerable quantities both of metallic salt and creosote can be injected into timber.

It has been stated that the elasticity of wood is increased by creosoting; the heart-wood only decays by oxidation.

The wood should be dried previous to undergoing the process, as the sapwood, otherwise almost useless, can be rendered serviceable, and for piles for marine work whole round timber should be used, because the sapwood is so much more readily saturated with the oil, and this prevents the worms from making an inroad into the heart.

Mr. Bethell uses about 10 lb. of creosote per cubic foot of wood, and he does not allow a piece of timber to be sent from his works without being tested to ascertain if it has absorbed that amount, or an amount previously agreed upon. We mention the latter statement, because it is evident that all descriptions of wood cannot be made to imbibe the same amount. This process is chiefly used for pine timber: yellow pine should absorb about 11 lb. to the cubic foot, and Riga pine about 9 lb. The quantity of oil recommended by the patentee, engineers, and others, is from 8 to 10 lb. for land purposes, and about 12 lb. to the cubic foot for marine. In this country, for marine the quantity does not exceed 12 lb.; but on the Continent, in France, Belgium, and Holland, the quantity used is from 14 to 22 lb. (!) per cubic foot. The specifications frequently issued by engineers for sleepers for foreign railways describe them to be entirely of heart-wood, and then to be creosoted to the extent of 10 lb. of the oil per cubic foot: this it is impossible to do, the value of the process being in the retention of the sapwood.

It being ascertained a few years since that the centres of some sleepers were not impregnated with the fluid, after the sleeper had been creosoted to the extent of 10 lb. of creosote per cubic foot, Sir Macdonald Stephenson suggested, as a means of obviating that defect, the boring of two holes, 1 inch in diameter, through each sleeper longitudinally, and impregnating up to 12 lb. or 14 lb. per cubic foot. By that means the creosote would be sent all through the sleeper. The boring by hand would be an expensive process, but by machinery it might be effected at a comparatively small increased cost.

During the last twenty-five years an enormous quantity of creosoted railway sleepers have been sent to India and other hot climates. The native woods are generally too hard for penetration. On the great Indian Peninsula Railway the native woods were so hard and close-grained that they could not be impregnated with any preservative substance, sál wood being principally used, into which creosote would not penetrate more than one quarter of an inch. As regards creosoting wood in India, it is moreover a costly process, owing to the difficulty and expense of conveying creosote from England; iron tanks are necessary to hold the oil when on board ship, and, being unsaleable in India, add to the expense.

English contractors often send piles to be creosoted which have been taken from the timber docks. The large quantity of water they contain resists the entrance of the oil, and the result is that a great deal of timber is badly prepared because the contractors cannot obtain it dry.

In the best creosoting works the tank or cylinder is about 6 feet diameter, and from 20 to 50 feet long. In some instances cylinders are open at both ends, and closed with iron doors, so that sleepers or timber entered at one end on being treated can be delivered finished at the opposite end; but for all practical purposes one open end is sufficient, as the oil when heated being of such a searching character it is a difficult matter to get the doors perfectly air-tight, consequently they are apt to leak during the time the pressure is being applied. Pipes are led from the cylinder to the air and force pumps; the air is not only extracted from the interior of the cylinder, but also from the pores of the timber. When a vacuum is made, the oil, which is contained in a tank below the cylinder, is allowed to rush in, and, as soon as the cylinder is full, the inlet pipe is shut and the pressure pumps started to force the oil into the wood; the pressure maintained is from 150 to 200 lb. to the square inch, until the wood has absorbed the required quantity of oil, which is learned by an index gauge fixed to the working tank below. All cylinders are fitted with safety valves, which allow the oil not immediately absorbed to pass again into the tank. The oil is heated by coils of pipe placed in the tank, through which a current of steam is passed from end to end, raising the temperature to 120°.

With regard to the cost of creosoting: half-round sleepers, being 9 feet long, 10 inches wide, and 5 inches thick, properly creosoted, are worth about 4s. each; adzing for the chairs (done by machine) costs 6s. per 100. These prices, unfortunately, vary very much, according to circumstances. The fir sleepers on the London and Birmingham Railway cost 7s. 6d. each, and the patent preservative added 9d. more to the expense, but they did not cost so much on other lines. A London builder wrote to us in 1870, as follows: “Our price for creosoting timber, &c., is 15s. per load of 50 cubic feet. Price of creosote, 2d. per gallon.”

By returns from the Leith Harbour Works it was shown that the average quantity of creosote absorbed by the timber was 57⅞ gallons per load, or 577 lb. weight forced into 50 cubic feet of wood. Assuming the cost to be 15s. per load, and the creosote at 2d. per gallon, the creosote would cost 9s. 8d., and the labour and profit 5s. 4d. per load of 50 cubic feet.

It is essential to observe that all methods of protecting timber depend for their success upon the skilful and conscientious manner in which they are applied; for, as they involve chemical actions on a large scale, their efficiency must depend upon the observance of the minute practical precautions required to exclude any disturbing causes. In the case of creosoting: to distil the creosote, to draw the sap or other moisture from the wood, and subsequently to inject the creosote in a proper manner, it is necessary that the operations should be carried into effect under the supervision of experienced persons of high character.

PATENT PRESERVATIVE SYSTEM.

Messrs. John Bethell and Cos. Timber preserving apparatus.

Mr. Bethell’s process has been and still is being tested on the Indian railways. According to Dr. Cleghorn, it appears that many of the creosoted sleepers have, however, “been found decayed in the centre, the interior portion being scooped out, leaving nothing but a deceptive shell, in some instances not more than ½ inch in thickness,” but he does not state whether the sleepers were prepared in England or in India; because, if prepared in India, it is probable that some of the hard Indian woods, into which it is not possible to get creosote or any other preservative fluid, had been used. Mr. Burt, who has large timber-preserving works in London for creosoting, stated about eight years since, that after an experience of twenty years, during which time he had sent over one million and a half sleepers to India alone, besides having prepared many thousand loads of timber for other purposes, he could safely assert that the instances of failure had been rare and isolated.

A section of a piece of timber impregnated with creosote presents some curious and very distinctive characteristics, according to the duration of the process of injection and amount of tar injected. In every case the injected tar follows the lines and sinuosities of the longitudinal fibres. When injected in sufficient quantity it fills the pores altogether; when, on the contrary, the process has been incompletely performed, which, however, is generally sufficient, the tar accumulates in the transverse sections, and plugs the channels that give access to deleterious agents.

The experiments made by M. Melseuns on oaken blocks exposed to the fumes of liquid ammonia show that the conservating fluids follow the precise course that would be taken by decay. In wood treated with creosote the tar acts on the very parts first exposed to injury, and on the course that would be taken by decay, which is thus rendered impossible. The methods of injection suggested by M. Melseuns in 1845 did not answer equally well with every kind of wood. After trying wooden blocks in every sort of condition, dressed and in the rough, green and dry, sound and decayed, M. Melseuns found that alder, birch, beech, hornbeam, and willow were easily and completely impregnated; deal sometimes resisted the process, the innermost layers remaining white; poplar and oak offered a very great resistance—indeed, with poplar it was found necessary to repeat the process.

The decay of sleepers, prepared and unprepared, will often depend on their form. Three forms have been used: 1st, the half-round sleeper, 10 inches by 5 inches; these are now almost universally used; 2nd, the triangular sleeper, about 12 inches wide on each side, used by Mr. Cubitt on the Dover line, but since abandoned; and 3rd, the half square, 14 inches by 7 inches, used by Mr. Brunel and still in use. Mr. G. O. Maun, in reporting on the state of the sleepers of the Pernambuco Railway, states that fair average samples taken out on the 1st December, 1863 (laid in 1857), show that the half-round intermediate sleeper is in the most perfect state of preservation; in fact, nearly as good as on the day it was put down; while the square-sawn or joint sleeper has not withstood the effects of the climate so well.

The kind of ballast in which it will be most advisable to lay the sleeper is another important point to be attended to. About 12 miles of the Pernambuco Railway are entirely laid with creosoted sleepers, principally in white sand. In this description of ballast the half-round sleepers have suffered, since the opening of the first section of the line in 1858 up to 1866, a depreciation of not more than 1 per cent., whilst the square-sawn sleepers have experienced a depreciation of not less than 50 per cent. Had the latter been placed in wet cuttings with ballast retentive of moisture, no doubt the whole of them would have required to be renewed. Hence it is evident that fine open sand ballast, which allows a free drainage during the rains, is best adapted for the preservation of sleepers in the tropics: it has also been found to be the best in most countries.

The number of testimonials given in favour of creosote is very large, and are from the most eminent engineers of all countries, in addition to which Mr. Bethell has received several medals at international exhibitions. The English engineers include Messrs. Brunel, Gregory, Abernethy, Ure, Hemans, Hawkshaw, and Cudworth; the French, MM. Molinos and Forestier; the Dutch, Messrs. Waldorp, Freem, and Von Baumhauer; and the Belgian, M. Crepin. The late Mr. Brunel expressly stated that, in his opinion, well creosoted timbers would be found in a sound and serviceable condition at the expiration of forty years. M. Forestier, French engineer of La Vendée department, reporting to the juries of the French Exhibition of 1867, cites a number of experiments he has lately tried upon many pieces of creosoted and uncreosoted oak, elm, ash, Swedish, Norwegian, and Dantzic red fir, Norway white fir, plane, and poplar, and shows that in each case, except that of the poplar, the resistance of the wood both to bending and crushing weight was much increased by creosoting.

Drs. Brande, Ure, and Letheby, also bear testimony to the efficacy of this mode of preserving timber.

Creosoting has been extensively employed upon all the principal railways in Great Britain. In England, upon the London and North Western, North Eastern, South Eastern, Great Western, &c. In Scotland, on the Caledonian, Great Northern, &c. In Ireland, on the Great Southern and Western, Midland, &c. It has also been and is being employed in Belgium, Holland, France, Prussia, India, and America.

Between the years 1838 and 1840, Sir William Burnett’s (formerly Director-General of the Medical Department of the Navy) process was first made known to the public.

This process consists of an injection of chloride of zinc into timber, in the proportion of about 1 lb. of the salt to about 9 or 10 gallons of water, forced into the wood under a pressure of 150 lb. per square inch.

The late Professor Graham thus wrote of its efficiency: “After making several experiments on wood prepared by the solution of chloride of zinc for the purpose of preservation, and having given the subject my best consideration, I have come to the following conclusions:

“The wood appears to be fully and deeply penetrated by the metallic salt. I have found it in the centre of a large prepared block.

“The salt, although very soluble, does not leave the wood easily when exposed to the weather, or buried in dry or damp earth. It does not come to the surface of the wood like the crystallizable salts. I have no doubt, indeed, that the greater part of the salts will remain in the wood for years, when employed for railway sleepers or such purposes. This may be of material consequence when the wood is exposed to the attacks of insects, such as the white ant in India, which, I believe, would be repelled by the poisonous metallic salt. After being long macerated in cold water, or even boiled in water, thin chips of the prepared wood retain a sensible quantity of the oxide of zinc; which I confirmed by Mr. Toplis’ test, and observed that the wood can be permanently dyed from being charged with a metallic mordant.

“I have no doubt, from repeated observations made during several years, of the valuable preservative qualities of the solution of chloride of zinc, as applied in Sir W. Burnett’s process; and would refer its beneficial action chiefly to the small quantity of the metallic salt, which is permanently retained by the ligneous fibre in all circumstances of exposure. The oxide of zinc appears to alter and harden the fibre of the wood, and destroy the solubility, and prevent the tendency to decomposition of the azotised principles it contains by entering into chemical combination with them.”

The Report of the Jury, which was drawn up by the Count of Westphalia, at the Cologne International Agricultural Exhibition, in 1865, upon prepared specimens of timber, has the following remarks on the chloride of zinc process:

1st. That chloride of zinc is the only substance which thoroughly penetrates the timber, and is at the same time the best adapted for its preservation.

2nd. That the process of impregnating the wood after cutting is more useful and rational than doing so while the tree is growing.

3rd. That red beech is the only wood which has been impregnated in an uniform and thorough manner.

It should, however, be stated that the Jury had very slender evidence presented to it respecting the creosoting process. The creosoted specimens had been impregnated under the pressure of 60 lb. to 65 lb. per square inch for three or four hours, and were consequently inefficiently done; in England the pressure per square inch would have been at least 140 lb.

Drs. Brande and Cooper, of England, and Dr. Cleghorn, of India, also wrote favourably of Sir W. Burnett’s process.

In 1847 a powerful cylinder, of Burnett’s construction, hermetically closed, was laid down adjoining the sawmills in Woolwich dockyard. It was found to admit the largest description of timber for the purpose of having the moisture extracted, and the pores filled with chloride of zinc. Three specimens of wood—English oak, English elm, and Dantzic fir—remained uninjured in the fungus pit at Woolwich for five years; while similar, but unprepared, specimens were all found more or less decayed.

The cost of preparing timber by this process is 12s. per load, besides 2s. for landing and loading: 1 lb. of the material costing 1s., which is sufficient for 9 or 10 gallons of water.

Sir W. Burnett and Co.’s works for hydraulic apparatus and tanks are at Nelson Wharf, Millwall, Poplar; their office is at 90, Cannon Street, London. Their terms are—

“For timber, round or square, including planks, deals, hop-poles, paving-blocks, &c., against rot, 12s. per load of 50 cubic feet.

“For park palings, cabinet work, wine and other laths, as per agreement.

“For railway sleepers, 9 feet long, 10 inches by 5 inches, landing and reshipping included, 7d. each.

“For timber to be rendered uninflammable, 25s. per load.”

Sir W. Burnett’s firm now sell their patent concentrated solution at 5s. per gallon: each gallon must be diluted with 40 gallons of water, according to the instructions in the licence, for which no charge is made.

The reader will probably have observed that this process is considered to render timber uninflammable; then let us see what will be the cost of obtaining a fire-proof house.

The principal building material which causes the destruction of our houses by fire is wood—combustible wood. If, therefore, (as nearly all our houses are “brick and timber” erections,) we render this wood uninflammable, what will the cost be?

The following is an approximate estimate of the extra expense, including sundries, &c.:—

Timber and Deals. Loads.	Cost of House. £	Additional expense. £
25	1000	34
15	600	21
10	400	14
8	250	12

When will the Building Act compel us to use this table in daily practice?

Although among the many attempts to preserve wood those in England have proved the most successful, it should be mentioned that France, Germany, and America have given much attention to the subject.

At the end of the last century Du Hamel and Buffon pointed out the possibility of preserving wood, as well as the means of rendering it unalterable. As early as 1758 Du Hamel made experiments on the vital suction of plants, and made some curious observations on the different rings of vegetable matter which absorb most liquid in different plants. He also tried the effect of vital suction and pressure (of gravitation) acting at the same time. His process was reviewed by Barral in 1842.

About 1784 M. Migneron invented a process about which little is now known, but the wood was covered with certain fatty substances. Wood nine years exposed to deterioration was improved by this process. M. Migneron had the approval of Buffon, Franklin, and the Academies. His invention was again brought into notice in 1807, when it was found that timber which had been prepared by it in 1784, and exposed more than twenty years, was quite sound.

In 1811 Cadet de Gassicourt made different kinds of wood imbibe vegetable and mineral substances, and certain unguents: he used metallic salts (iron, tin, &c.).

In 1813 M. Champy plunged wood into a bath of tallow at 334°, and kept it there two or three hours. His experiments were afterwards repeated by Mr. Payne.

About the year 1832 it was proposed in America to apply pyroligneous acid to the surface of wood, or introduce it by fumigation.

Biot (who has written an excellent life of Sir Isaac Newton) remarked, in 1831, that wood could be soaked by pressure; but his process of penetrating it with liquids was imperfect, and his discovery remains unapplied.

A Frenchman, of the name of Bréant, made about this time a discovery which preceded Boucherie’s method, which is adopted to a great extent in France. Bréant’s apparatus consisted of a very ingenious machine, which, acting by pressure, caused liquids to penetrate to all points of a mass of wood of great diameter and considerable length. He may therefore be regarded as having solved the problem of penetration in a scientific, though not in a practically applied, point of view. Dr. Boucherie testified before the Académie des Sciences, in 1840, to the merit of Bréant’s invention, which, with modifications by Payne, Brochard, and Gemini, has been worked in France and England. This process was recommended by Payne in 1840 and 1844, and imitated by him in France, and later on by Yengat and Bauner, who used both an air pump and a forcing pump. Bréant obtained three patents, viz. 1st, in 1831, to act by pressure; 2nd, in 1837, by vital suction: and 3rd, in 1838, vacuum by steam. A mixture of linseed oil and resin succeeded best with him. He attached more importance to the thorough penetration of the wood than to the choice of the penetrating substances. He borrowed his process from Du Hamel, but to make the necessary suction in the pores he produces a partial vacuum in the impregnating cylinder by filling it with steam, and condensing the steam.

Previous to Boucherie’s method, a German, Frantz Moll, in 1835, proposed to introduce into wood creosote in a state of vapour, but the process was found to be too expensive. This was a modification of Maconochie and Lukin’s trials in 1805 and 1811.[11] A similar process has since arisen in New York: we believe Mr. Renwick, of that place, suggested it.

Such were the known labours, when Dr. Boucherie, in December, 1837, devoted his time to a series of experiments upon timber, with a view to discover some preservative process which should answer the following requirements: First, for protecting wood from dry rot or wet rot; second, for increasing its hardness; third, for preserving and developing its flexibility and elasticity; fourth, for preventing its decay, and the fissures that result from it, when, after having been used in construction, it is left exposed to the variations of the atmosphere; fifth, for giving it various and enduring colours and odours; and sixth and last, for greatly reducing its inflammability.

It is a curious coincidence that at Bordeaux, in 1733, the Academy received a memoir relative to the circulation of the sap and coloured liquids in plants; and it was at Bordeaux, a century afterwards, viz. 1837, that M. Boucherie first mentioned his method.

M. Boucherie’s process was first discussed in Paris in June, 1840. It consists in causing a solution of sulphate of copper to penetrate to the interior of freshly cut woods, to preserve them from decay; he occasionally used the chloride of calcium, the pyrolignite of iron (pyrolignite brut de fer), prussiate of iron, prussiate of copper, and various other metallic salts. As a general rule sulphate of copper is used; but when the hardness of the wood is desired to be increased, pyrolignite of iron is taken (1 gallon of iron to 6 gallons of water); and when the object is to render the wood flexible, elastic, and at the same time uninflammable, chloride of calcium is used. The liquid is taken up by the tree either whilst growing in the earth or immediately after it has been felled. Not more than two or three months should be allowed to elapse before the timber is operated upon, but the sooner it undergoes the process after being felled the better.

Sulphate of copper is said to be superior to corrosive sublimate. Dr. Boucherie’s process of the injection of wood with the salts of copper is as simple as it is easy. For those woods intended for poles it consists in plunging the base of a branch, furnished with leaves, into a tub containing the solution. The liquid ascends into the branches by the action of the leaves, and the wood is impregnated with the preservative salt. As for logs, the operation consists in cutting down the tree to be operated upon; fixing at its base a plank, which is fixed by means of a screw placed in the centre, and which can be tightened at will when placed in the centre of the tree. This plank has, on the side to be applied to the bottom of the tree, a rather thick shield of leather, cloth, pasteboard, or some other substance, intended to establish a space between it and the wood, sufficient for the preserving fluid to keep in contact with the freshly cut surface of the tree. The liquid is brought there from a tub or other reservoir, by the help of a slanting pole made on the upper surface of the tree, and in which is put a tube, adapted at its other extremity to a spigot in the upper reservoir which contains the solution. A pressure of 5 mètres suffices; so that the instant the sap of the tree is drawn away it escapes, and is replaced by the liquid saturated with sulphate of copper. The proportion of sulphate of copper in the solution should be 1 lb. of the salt to 12½ gallons of water. As soon as the operation terminates (and it lasts for some hours for the most difficult logs), the wood is ready for use.

For various practical reasons, the first invention of impregnating the wood of the tree whilst still in a growing state, causing it to suck up various solutions by means of the absorbing power of the leaves themselves, was subsequently abandoned; and at the present time a cheap, simple, and effective process is adopted for impregnating the felled timbers with the preserving liquid, designated in France “trait de scie, et la cuisse foulante.” The trunk of a newly felled tree is cut into a length suitable for two railway sleepers; a cross cut is made on the prostrate timber to nearly nine-tenths of its diameter; a wedge is then inserted, and a cord is wound round on the cut surface, leaving a shallow chamber in the centre, when it is then closed by withdrawing the wedge. A tube is then inserted through an auger hole into this chamber, and to this tube is attached an elastic connecting tube from a reservoir placed some 20 or 30 feet above the level on which the wood lies, and a stream of the saturating fluid with this pressure passes into the chamber, presses on the sap in the sap tubes, expels it at each end of the tree, and itself supplies its place. The fluid used is a solution of copper in water, in the proportion of 10 or 12 per cent., and a chemical test that ascertains the pressure of the copper solution is applied at each end of the tree from which the sap exudes, by which the operator ascertains when the process is completed.

A full account of this process may be found in the number for June, 1840, of ‘Les Annales de Chimie et de Physique.’ Messrs. de Mirbel, Arago, Poucelet, Andouin, Gambey, Boussingault, and Dumas, on the part of l’Académie des Sciences, made a report upon Dr. Boucherie’s process, confirming the value of the invention. In France, Dr. Boucherie, some years since, relinquished his brévet, and threw the process open to the public, in consideration of a national reward; whilst in England he has obtained two patents (1838 and 1841), which, however, are similar to Bethell’s patent, obtained by him on July 11, 1838: which is the same day and year of Boucherie’s patent. A prize medal was awarded for Dr. Boucherie’s process at the Great Exhibition in London, in 1851, and a grande médaille d’honneur, at the Paris Exhibition of 1855. Many thousands of railway sleepers have been prepared by this process, and laid down on the Great Northern Railway of France, and are at present perfectly sound, whilst others not prepared, on the same line, have rotted. Boucherie’s process was used on Belgium railways up to 1859; and it is to be regretted that the reasons which led to its abandonment have not been given in the reports of the railway administration, as such reasons would have afforded reliable data for future experimentalists to go upon.

Messrs. Légé and Fleury-Pironnet’s patent for the injection of sulphate of copper into beech and poplar is as follows: After the wood is placed, and the opening hermetically sealed, a jet of steam is introduced, intended at first to enter the timber and open its pores for the purpose of obtaining a sudden vacuum, so as to establish at any time a communication between the interior of the cylinder and the cold water condenser; at the same time the air pump is put in action. The vacuum caused is very powerful, and is equal to 25½ ins. of the barometer. Under the double influence of the heat and the vacuum the sap is quickly evaporated from the wood as steam, and ejected from the cylinder by the air pump, so that in a very short time the wood is fully prepared to admit the preserving liquid through the entire bulk.

The use of sulphate of copper for preserving timber has not been, however, confined to France, for about the time Dr. Boucherie brought forward his process, a Mr. Margary took out a patent in England for the use of the same material. His method consists in steeping the substances to be preserved in a solution of sulphate of copper, of the strength of 1 lb. of the sulphate to 8 gallons of water, and leaving them in it till thoroughly saturated. The timber is allowed to remain in the tank two days for every inch of its thickness. Another method is to place the timber in a closed iron vessel of great strength, and it is made to imbibe the solution by exhaustion and pressure, the operation occupying but a short time.

Sulphate of copper is sold in quantities at 4d. per lb.; so that 100l. would buy 6000 lb., and each pound weight is sufficient for 7 or 8 gallons of water, according to Margary; or 12 gallons of water, according to Boucherie.

To preserve railway sleepers, the French railway engineers require ¼ lb. of sulphate of copper per cubic foot, say at least 12 lbs. to the load of 50 feet, to be used in a 2 per cent. solution; so that a load of timber can be rendered imperishable for the sum of four shillings, exclusive of labour, if sulphate of copper be reckoned at 4d. per lb.

With respect to the use of pyrolignite of iron, Mr. Bethell considers it an expensive process, the pyrolignite costing 6d. to 9d. per gallon, whilst the oil of tar can be delivered at from 2d. to 3d. per gallon: the cost of these materials is constantly varying.

A great many sleepers were prepared on the Great Western Railway by pyrolignite of iron, and all have decayed. Their black colour makes them exactly resemble creosoted sleepers, and many mistakes have arisen from this resemblance.

Messrs. Dorsett and Blythé’s (of Bordeaux) patent process of preparing wood by the injection of heated solutions of sulphate of copper is said to have been adopted by French, Spanish, and Italian, as well as other continental railway companies, by the French Government for their navy and other constructions, and by telegraph companies for poles on continental lines. It is as cheap as creosote, and is employed in places where creosote cannot be had. Wood prepared by it is rendered incombustible. Wood for outdoor purposes so prepared has a clean yellowish surface, without odour; it requires no painting, remains unchangeable for any length of time, and can be employed for any purpose, the same as unprepared material, and carried with other cargo without hindrance.[12] Messrs. Dorsett and Blythé’s process is similar to that of Mr. Knab, which consisted of a solution of sulphate of copper, heated to nearly boiling point, and placed in a lead cylinder, protected by wood.

In 1846, 80,000 sleepers, treated with sulphate of copper, were laid down on French railways, and after nine years’ exposure were found to be as perfect as when first laid.

Mr. H. W. Lewis, University of Michigan, U.S., thus writes in the ‘Journal’ of the Franklin Institute, in 1866, with reference to the decay of American railway sleepers: “Allowing 2112 sleepers per mile, at 50 cents each, 1056 dols. per mile of American railroad decay every seven years. Thoroughly impregnate those sleepers with sulphate of copper, at a cost of 5 cents each, and they would last twice as long. Thus would be effected a saving of 880 dols. per mile in the seven years on sleepers alone. In the United States, there are 33,906·6 miles of railroad. The whole saving on these lines would be 29,389,568 dols., or upwards of 4,262,795 dols. per annum.”

With reference to the decay of unprepared wooden sleepers, it may be here stated that the renewal of wooden sleepers on the Calcutta and Delhi Indian line alone costs annually 130,000l.

The preservative action of sulphate of copper on wood has long been known, but there are several things in its action which require explanation. The ‘London Review’ says that Kœnig has lately investigated the chemical reactions which occur when wood is impregnated with a preservative solution of blue vitriol. He finds, as a general rule, that a certain quantity of basic sulphate of copper remains combined in the pores of the wood in such a manner that it cannot be washed out with water. The copper salt may be seen by its green colour in the spaces between the yearly rings in the less compact portions of the wood, that is to say, in those portions which contain the sap. Those varieties of wood which contain the most resin retain the largest amount of the copper salt—oak, for example, retaining but little of it. The ligneous fibre itself appears to have little or nothing to do with the fluxation of the copper salt, and indeed none whatever is retained in chemical combination, so that it cannot be washed out with water, by pure cellulose. When wood, from which all resin has been extracted by boiling alcohol, is impregnated with sulphate of copper, it does not become coloured like the original resinous wood, and the copper salt contained in it may be readily washed out with water. In like manner, from impregnated resinous wood all the copper salt may be removed, with the resin, by means of alcohol. The constituents of the blue vitriol are consequently fixed in the wood by means of the resin which this contains. Further, it is found that the impregnated wood contains less nitrogen than that which is unimpregnated, and that it is even possible to remove all the nitrogenous components of the wood by long-continued treatment with the solution of sulphate of copper; the nitrogenous matters being soluble in an excess of this solution, just as the precipitate which forms when aqueous solutions of albumen and sulphate of copper are mixed is soluble in excess of the latter. Since the nitrogenous matters are well known to be promoters of putrefaction, their removal readily accounts for the increased durability of the impregnated wood. The utility of blue vitriol as a preservative may also depend on a measure upon the resinous copper salt which is formed, by which the pores of the wood are more or less filled up, and the ligneous fibre covered, so that contact with the air is prevented, and the attack of insects hindered. It is suggested that those cases in which the anticipated benefits have not been realized in practice, by impregnating wood with a solution of blue vitriol, may probably be referred to the use of an insufficient amount of this agent; that is, where the wood was not immersed in the solution for a sufficient length of time. The action should be one of lixiviation, not merely of absorption.

In 1841, a German, named Müenzing, a chemist of Heibronn, proposed chloride of manganese (waste liquor in the manufacture of bleaching powder) as a preservative against dry rot in timber; but his process has not been adopted in England, and very little noticed abroad.

In July, 1841, Mr. Payne patented his invention for sulphate of iron in London; and in June and November, 1846, in France; and in 1846 in London, for carbonate of soda.[13] The materials employed in Payne’s process are sulphate of iron and sulphate of lime, both being held in solution with water. The timber is placed in a cylinder in which a vacuum is formed by the condensation of steam, assisted by air pumps; a solution of sulphate of iron is then admitted into the vessel, which instantly insinuates itself into all the pores of the wood, previously freed from air by the vacuum, and, after about a minute’s exposure, impregnates its entire substance; the sulphate of iron is then withdrawn, and another solution of sulphate of lime thrown in, which enters the substance of the wood in the same manner as the former solution, and the two salts react upon each other, and form two new combinations within the substance of the wood—muriate of iron, and muriate of lime. One of the most valuable properties of timber thus prepared is its perfect incombustibility: when exposed to the action of flame or strong heat, it simply smoulders, and emits no flame. We may also reasonably infer that with such a compound in its pores, decay must be greatly retarded, and the liability to worms lessened, if not prevented. The greatest drawback consists in the increased difficulty of working. This invention has been approved by the Commissioners of Woods and Forests, and has received much approbation from the architectural profession. Mr. Hawkshaw, C.E., considers that this process renders wood brittle. It was employed for rendering wood uninflammable in the Houses of Parliament (we presume, in the carcase; for steaming was used for the joiner’s work), British Museum, and other public buildings; and also for the Royal Stables at Claremont.

In 1842, Mr. Bethell stated before the Institute of Civil Engineers, London, that silicate of potash, or soluble glass, rendered wood uninflammable.

In 1842, Professor Brande proposed corrosive sublimate in turpentine, or oil of tar, as a preservative solution.

In 1845, Mr. Ransome suggested the application of silicate of soda, to be afterwards decomposed by an acid in the fibre of the wood; and in 1846, Mr Payne proposed soluble sulphides of the earth (barium sulphide, &c.), to be also afterwards decomposed in the woods by acids.

In 1855, a writer in the ‘Builder’ suggested an equal mixture of alum and borax (biborate of soda) to be used for making wood uninflammable. We have no objection to the use of alum and borax to render wood uninflammable, providing it does not hurt the wood.

Such are the principal patents, suggestions, and inventions, up to the year 1856; but there are many more which have been brought before the public, some of which we will now describe.

Dr. Darwin, some years since, proposed absorption, first, of lime water, then of a weak solution of sulphuric acid, drying between the two, so as to form a gypsum (sulphate of lime) in the pores of the wood, the latter to be previously well seasoned, and when prepared to be used in a dry situation.

Dr. Parry has recommended a preparation composed of bees-wax, roll brimstone, and oil, in the proportion of 1, 2, and 3 ounces to ¾ gallon of water; to be boiled together and laid on hot.

Mr. Pritchard, C.E., of Shoreham, succeeded in establishing pyrolignite of iron and oil of tar as a preventive of dry rot; the pyrolignite to be used very pure, the oil applied afterwards, and to be perfectly free from any particle of ammonia.

Mr. Toplis recommends the introduction into the pores of the timber of a solution of sulphate or muriate of iron; the solution may be in the proportion of about 2 lb. of the salt to 4 or 5 gallons of water.

An invention has been lately patented by Mr. John Cullen, of the North London Railway, Bow, for preserving wood from decay. The inventor proposes to use a composition of coal-tar, lime, and charcoal; the charcoal to be reduced to a fine powder, and also the lime. These materials to be well mixed, and subjected to heat, and the wood immersed therein. The impregnation of the wood with the composition may be materially aided by means of exhaustion and pressure. Wood thus prepared is considered to be proof against the attacks of the white ant.

The process of preserving wood from decay invented by Mr. L. S. Robins, of New York, was proposed to be worked extensively by the “British Patent Wood Preserving Company.” It consists in first removing the surface moisture, and then charging and saturating the wood with hot oleaginous vapours and compounds. As the Robins’ process applies the preserving material in the form of vapour, the wood is left clean, and after a few hours’ exposure to the air it is said to be fit to be handled for any purposes in which elegant workmanship is required. Neither science nor extraordinary skill is required in conducting the process, and the treatment under the patent is said to involve only a trifling expense.

Reference has already been made to the use of petroleum. The almost unlimited supply of it within the last few years has opened out a new and almost boundless source of wealth. An invention has been patented in the name of Mr. A. Prince, which purports to be an improvement in the mode of preserving timber by the aid of petroleum. The invention consists, firstly, in the immersion of the timber in a suitable vessel or receptacle, and to exhaust the air therefrom, by the ordinary means of preserving wood by saturation. The crude petroleum is next conveyed into the vessel, and thereby caused to penetrate into every pore or interstice of the woody fibre, the effect being, it is said, to thoroughly preserve the wood from decay. He also proposes to mix any cheap mineral paint or pigment with crude petroleum to be used as a coating for the bottom of ships before the application of the sheathing, and also to all timber for building or other purposes. The composition is considered to render the timber indestructible, and to repel the attacks of insects. Without expressing any opinion upon this patent as applied to wood for building purposes, we must again draw attention to the high inflammability of petroleum.

The ‘Journal’ of the Board of Arts and Manufactures for Upper Canada considers the following to be the cheapest and the best mode of preserving timber in Canada: Let the timbers be placed in a drying chamber for a few hours, where they would be exposed to a temperature of about 200°, so as to drive out all moisture, and by heat, coagulate the albuminous substance, which is so productive of decay. Immediately upon being taken out of the drying chamber, they should be thrown into a tank containing crude petroleum. As the wood cools, the air in the pores will contract, and the petroleum occupy the place it filled. Such is the extraordinary attraction shown by this substance for dry surfaces, that by the process called capillary attraction, it would gradually find its way into the interior of the largest pieces of timber, and effectually coat the walls and cells, and interstitial spaces. During the lapse of time, the petroleum would absorb oxygen, and become inspissated, and finally converted into a bituminous substance, which would effectually shield the wood from destruction by the ordinary processes of decay. The process commends itself on account of its cheapness. A drying chamber might easily be constructed of sheet iron properly strengthened, and petroleum is very abundant and accessible. Immediately after the pieces of timber have been taken out of the petroleum vat, they should be sprinkled with wood ashes in order that a coating of this substance may adhere to the surface, and carbonate of potash be absorbed to a small depth. The object of this is to render the surface incombustible; and dusting with wood ashes until quite dry will destroy this property to a certain extent.

The woodwork of farm buildings in this country is sometimes subjected to the following: Take two parts of gas-tar, one part of pitch, one part half caustic lime and half common resin; mix and boil these well together, and put them on the wood quite hot. Apply two or three coats, and while the last coat is still warm, dash on it a quantity of well-washed sharp sand, previously prepared by being sifted through a sieve. The surface of the wood will then have a complete stone appearance, and may be durable. It is, of course, necessary, that the wood be perfectly dry, and one coat should be well hardened before the next is put on. It is necessary, by the use of lime and long boiling, to get quit of the ammonia of the tar, as it is considered to injure the wood.

Mr. Abel, the eminent chemist to the War Department, recommends the application of silicate of soda in solution, for giving to wood, when applied to it like paint, a hard coating, which is durable for several years, and is also a considerable protection against fire. The silicate of soda, which is prepared for use in the form of a thick syrup, is diluted in water in the proportion of 1 part by measure of the syrup to 4 parts of water, which is added slowly, until a perfect mixture is obtained by constant stirring. The wood is then washed over two or three times with this liquid by means of an ordinary whitewash brush, so as to absorb as much of it as possible. When this first coating is nearly dry, the wood is painted over with another wash made by slaking good fat lime, diluted to the consistency of thick cream. Then, after the limewash has become moderately dry, another solution of the silicate of soda, in the proportion of 1 of soda to 2 of water, is applied in the same manner as the first coating. The preparation of the wood is then complete; but if the lime coating has been applied too quickly, the surface of the wood may be found, when quite dry, after the last coating of the silicate, to give off a little lime when rubbed with the hand; in which case it should be once more coated over with a solution of the silicate of the same strength as in the first operation. If Mr. Abel had been an architect or builder, he would never have invented this process. What would the cost be? and would not a special clerk of the works be necessary to carry out this method in practice?

The following coating for piles and posts, to prevent them from rotting, has been recommended on account of its being economical, impermeable to water, and nearly as hard as stone: Take 50 parts of resin, 40 of finely powdered chalk, 300 parts of fine white sharp sand, 4 parts of linseed oil, 1 part of native red oxide of copper, and 1 part of sulphuric acid. First, heat the resin, chalk, sand, and oil, in an iron boiler; then add the oxide, and, with care, the acid; stir the composition carefully, and apply the coat while it is still hot. If it be not liquid enough, add a little more oil. This coating, when it is cold and dry, forms a varnish which is as hard as stone.

Another method for fencing, gate-posts, garden stakes, and timber which is to be buried in the earth, may be mentioned. Take 11 lb. of blue vitriol (sulphate of copper) and 20 quarts of water; dissolve the vitriol with boiling water, and then add the remainder of the water. The end of the wood is then to be put into the solution, and left to stand four or five days; for shingle, three days will answer, and for posts, 6 inches square, ten days, Care should be taken that the saturation takes place in a well-pitched tank or keyed box, for the reason that any barrel will be shrunk by the operation so as to leak. Instead of expanding an old cask, as other liquids do, this shrinks it. This solution has also been used in dry rot cases, when the wood is only slightly affected.

It will sometimes be found that when oak fencing is put up new, and tarred or painted, a fungus will vegetate through the dressing, and the interior of the wood be rapidly destroyed; but when undressed it seems that the weather desiccates the gum or sap, and leaves only the woody fibre, and the fence lasts for many years.

About fifteen years ago, Professor Crace Calvert, F.R.S., made an investigation for the Admiralty, of the qualities of different woods used in ship-building. He found the goodness of teak to consist in the fact that it is highly charged with caoutchouc; and he considered that if the tannin be soaked out of a block of oak, it may then be interpenetrated by a solution of caoutchouc, and thereby rendered as lasting as teak.

We can only spare the space for a few words about this method.

1st. We have seen lead which has formed part of the gutter of a building previous to its being burnt down: lead melts at 612° F.; caoutchouc at 248° F.; therefore caoutchouc would not prevent wood from being destroyed by fire. At 248° caoutchouc is highly inflammable, burns with a white flame and much smoke.

2nd. We are informed by a surgical bandage-maker of high repute, that caoutchouc, when used in elastic kneecaps, &c., will perish, if the articles are left in a drawer for two or three years. When hard, caoutchouc is brittle.

Would it be advisable to interpenetrate oak with a solution of caoutchouc? In 1825, Mr. Hancock proposed a solution of 1½ lb. of caoutchouc in 3 lb. of essential oil, to which was to be added 9 lb. of tar. Mr. Parkes, in 1843, and M. Passez, in 1845, proposed to dissolve caoutchouc in sulphur: painting or immersing the wood. Maconochie, in 1805, after his return from India, proposed distilled teak chips to be injected into fir woods.

Although England has been active in endeavouring to discover the best and cheapest remedy for dry rot, France has also been active in the same direction.

M. le Comte de Chassloup Lambat, Member of the late Imperial Senate of France, considers that, as sulphur is most prejudicial to all species of fungi, there might, perhaps, be some means of making it serviceable in the preservation of timber. We know with what success it is used in medicine. It is also known that coopers burn a sulphur match in old casks before using them—a practice which has evidently for its object the prevention of mustiness, often microscopic, which would impart a bad flavour to the wine.

M. de Lapparent, late Inspector-General of Timber for the French Navy, proposed to prevent the growth of fungi by the use of a paint having flour of sulphur as a basis, and linseed oil as an amalgamater. In 1862 he proposed charring wood; we have referred to this process in our last chapter (p. 96).

The paint was to be composed of:

Flour of sulphur	200	grammes	3,088	grains.
Common linseed oil	135	”	2,084	”
Prepared oil of manganese	30	”	463	”

He considered that by smearing here and there either the surfaces of the ribs of a ship, or below the ceiling, with this paint, a slightly sulphurous atmosphere will be developed in the hold, which will purify the air by destroying, at least in part, the sporules of the fungi. He has since stated that his anticipations have been fully realized. M. de Lapparent also proposes to prevent the decay of timber by subjecting it to a skilful carbonization with common inflammable coal gas. An experiment was made at Cherbourg, which was stated to be completely successful. The cost is only about 10 cents per square yard of framing and planking.[14] M. de Lapparent’s gas method is useful for burning off old paint. We saw it in practice (April, 1875) at Waterloo Railway Station, London, and it appeared to be effective.

At the suggestion of MM. Le Châtelier (Engineer-in-chief of mines) and Flachat, C.E.’s, M. Ranee, a few years since, injected in a Légé and Fleury cylinder certain pieces of white fir, red fir, and pitch pine with chloride of sodium, which had been deprived of the manganesian salts it contained, to destroy its deliquescent property. Some pieces were injected four times, but the greatest amount of solution injected into pitch pine heart-wood was from 3 to 4 per cent., and very little more was injected into the white and red fir heart-wood. It was also noticed that sapwood, after being injected four times, only gained 8 per cent. in weight in the last three operations. The experiments made to test the relative incombustibility of the injected wood showed that the process was a complete failure; the prepared wood burning as quickly as the unprepared wood.

M. Paschal le Gros, of Paris, has patented his system for preserving all kinds of wood, by means of a double salt of manganese and of zinc, used either alone or with an admixture of creosote. The solution, obtained in either of the two ways, is poured into a trough, and the immersion of the logs or pieces of wood is effected by placing them vertically in the trough in such a manner that they are steeped in the liquid to about three-quarters of their length. The wood is thus subjected to the action of the solution during a length of time varying from twelve to forty-eight hours. The solution rises in the fibres of the wood, and impregnates them by the capillary force alone, without requiring any mechanical action. The timber is said to become incombustible, hard, and very lasting.

M. Fontenay, C.E., in 1832, proposed to act upon the wood with what he designated metallic soap, which could be obtained from the residue in greasing boxes of carriages; also from the acid remains of oil, suet, iron, and brass dust; all being melted together. In 1816 Chapman tried experiments with yellow soap; but to render it sufficiently fluid it required forty times its weight of water, in which the quantity of resinous matter and tallow would scarcely exceed ⅟80th; therefore no greater portion of these substances could be left in the pores of the wood, which could produce little effect.

M. Letellier, in 1837, proposed to use deuto-chloride of mercury as a preservative for wood.

M. Dondeine’s process was formerly used in France and Germany. It is a paint, consisting of many ingredients, the principal being linseed oil, resin, white lead, vermilion, lard, and oxide of iron. All these are to be well mixed, and reduced by boiling to one-tenth, and then applied with a brush. If applied cold, a little varnish or turpentine to be added.

Little is known in England of the inventions which have arisen in foreign countries not already mentioned.

M. Szerelmey, a Hungarian, proposed, in 1868, potassa, lime, sulphuric acid, petroleum, &c., to preserve wood.

In Germany, the following method is sometimes used for the preservation of wood: Mix 40 parts of chalk, 40 parts of resin, 4 of linseed oil; melting them together in an iron pot; then add 1 part of native oxide of copper, and afterwards, carefully, 1 part of sulphuric acid. The mixture is applied while hot to the wood by means of a brush, and it soon becomes very hard.[15]

Mr. Cobley, of Meerholz, Hesse, has patented the following preparation. A strong solution of potash, baryta, lime, strontia, or any of their salts, are forced into the pores of timber in a close iron vessel by a pump. After this operation, the liquid is run off from the timber, and hydro-fluo-silicic acid is forced in, which, uniting with the salts in the timber, forms an insoluble compound capable of rendering the wood uninflammable.

About the year 1800, Neils Nystrom, chemist, Norkopping, recommended a solution of sea salt and copperas, to be laid upon timber as hot as possible, to prevent rottenness or combustion. He also proposed a solution of sulphate of iron, potash, alum, &c., to extinguish fires.

M. Louis Vernet, Buenos Ayres, proposed to preserve timber from fire by the use of the following mixture: Take 1 lb. of arsenic, 6 lb. of alum, and 10 lb. of potash, in 40 gallons of water, and mix with oil, or any suitable tarry matters, and paint the timber with the solution. We have already referred to the conflicting evidence respecting alum and water for wood: we can now state that Chapman’s experiments proved that arsenic afforded no protection against dry rot. Experiments in Cornwall have proved that where arsenical ores have lain on the ground, vegetation will ensue in two or three years after removal of the ore. If, therefore, alum or arsenic have no good effect on timber with respect to the dry rot, we think the use of both of them together would certainly be objectionable.

The last we intend referring to is a composition frequently used in China, for preserving wood. Many buildings in the capital are painted with it. It is called Schoicao, and is made with 3 parts of blood deprived of its febrine, 4 parts of lime and a little alum, and 2 parts of liquid silicate of soda. It is sometimes used in Japan.

It would be practically useless to quote any further remedies, and the reader is recommended to carefully study those quoted in this chapter, and of their utility to judge for himself, bearing in mind those principles which we have referred to before commencing to describe the patent processes. A large number of patents have been taken out in England for the preservation of wood by preservative processes, but only two are now in use,—that is, to any extent,—viz. Bethell’s and Burnett’s. Messrs. Bethell and Co. now impregnate timber with copper, zinc, corrosive sublimate, or creosote; the four best patents.

We insert here a short analysis of different methods proposed for seasoning timber:—

Vacuum and Pressure Processes generally.

• Bréant’s.
• Bethell’s.
• Payne’s.
• Perin’s.
• Tissier’s.

Vacuum by Condensation of Steam.

• Tissier.
• Bréant.
• Payne.
• Renard Perin, 1848.
• Brochard and Watteau, 1847.

Separate Condenser.

• Tissier.

Employ Sulphate of Copper in closed vessels.

• Bethell’s Patent, 11th July, 1838.
• Tissier, 22nd October, 1844.
• Molin’s Paper, 1853.
• Payen’s Pamphlet.
• Légé and Fleury’s Pamphlet.

Current of Steam.

• Moll’s Patent, 19th January, 1835.
• Tissier’s ” 22nd October, 1844.
• Payne’s ” 14th Nov., 1846.
• Meyer d’Uslaw, 2nd January, 1851.
• Payen’s Pamphlet.

Hot Solution.

• Tissier’s Patent, 22nd October, 1844.
• Knab’s Patent, 8th September, 1846.

Most solutions used are heated.

The following are the chief ingredients which have been recommended, and some of them tried, to prevent the decomposition of timber, and the growth of fungi:—

• Acid, Sulphuric.
• ” Vitriolic.
• ” of Tar.
• Carbonate of Potash.
• ” Soda.
• ” Barytes.
• Sulphate of Copper.
• ” Iron.
• ” Zinc.
• ” Lime.
• ” Magnesia.
• ” Barytes.
• ” Alumina.
• ” Soda.
• Salt, Neutral.
• Salt, Selenites.
• Oil, Vegetable.
• ” Animal.
• ” Mineral.
• Muriate of Soda.
• Marcosites, Mundic.
• ” Barytes.
• Nitrate of Potash.
• Animal Glue.
• ” Wax.
• Quick Lime.
• Resins of different kinds.
• Sublimate, Corrosive.
• Peat Moss.

For the non-professional reader we find we have three facts:

1st. The most successful patentees have been Bethell and Burnett, in England; and Boucherie, in France: all B’s.

2nd. The most successful patents have been knighted. Payne’s patent was, we believe, used by Sirs R. Smirke and C. Barry; Kyan’s, by Sir R. Smirke; Burnett’s, by Sirs M. Peto, P. Roney, and H. Dryden; while Bethell’s patent can claim Sir I. Brunel, and many other knights. We believe Dr. Boucherie received the Legion of Honour in France.

3rd. There are only at the present time three timber-preserving works in London, and they are owned by Messrs. Bethell and Co., Sir F. Burnett and Co., and Messrs. Burt, Boulton, and Co.: all names commencing with the letter B.

For the professional reader we find we have three hard facts:

The most successful patents may be placed in three classes, and we give the key-note of their success.

1st. One material and one application.—Creosote, Petroleum. Order—Ancient Egyptians, or Bethell’s, Burmese.

2nd. Two materials and one application.—Chloride of zinc and water; sulphate of copper and water; corrosive sublimate and water. Order—Burnett, Boucherie, Kyan.

3rd. Two materials and two applications.—Sulphate of iron and water; afterwards sulphate of lime and water. Payne.

We thus observe there are twice three successful patent processes.

Any inventions which cannot be brought under these three classes have had a short life; at least, we think so.

The same remarks will apply to external applications for wood—for instance, coal-tar, one application, is more used for fencing than any other material.

We are much in want of a valuable series of experiments on the application of various chemicals on wood to resist burning to pieces; without causing it to rot speedily.

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CHAPTER VI.
ON THE MEANS OF PREVENTING DRY ROT IN MODERN HOUSES; AND THE CAUSES OF THEIR DECAY.

Although writers on dry rot have generally deemed it a new disease, there is foundation to believe that it pervaded the British Navy in the reign of Charles II. “Dry rot received a little attention” so writes Sir John Barrow, “about the middle of the last century, at some period of Sir John Pringle’s presidency of the Royal Society of London.” As timber trees were, no doubt, subject to the same laws and conditions 500 years ago as they are at the present day, it is indeed extremely probable that if at that time unseasoned timber was used, and subjected to heat and moisture, dry rot made its appearance. We propose in this chapter to direct attention to the several causes of the decay of wood, which by proper building might be averted.

The necessity of proper ventilation round the timbers of a building has been repeatedly advised in this volume; for even timber which has been naturally seasoned is at all times disposed to resume, from a warm and stagnant atmosphere, the elements of decay. We cannot therefore agree with the following passage from Captain E. M. Shaw’s book on ‘Fire Surveys,’ which is to be found at page 44:—“Circulation of air should on no account be permitted in any part of a building not exposed to view, especially under floors, or inside skirting boards, or wainscots.” In the course of this chapter, the evil results from a want of a proper circulation of air will be shown.

In warm cellars, or any close confined situations, where the air is filled with vapour without a current to change it, dry rot proceeds with astonishing rapidity, and the timber work is destroyed in a very short time. The bread rooms of ships; behind the skirtings, and under the wooden floors, or the basement stories of houses, particularly in kitchens, or other rooms where there are constant fires; and, in general, in every place where wood is exposed to warmth and damp air, the dry rot will soon make its appearance.

All kinds of stoves are sure to increase the disease if moisture be present. The effect of heat is also evident from the rapid decay of ships in hot climates; and the warm moisture given out by particular cargoes is also very destructive. Hemp will, without being injuriously heated, emit a moist warm vapour: so will pepper (which will affect teak) and cotton. The ship ‘Brothers’ built at Whitby, of green timber, proceeded to St. Petersburgh for a cargo of hemp. The next year it was found on examination that her timbers were rotten, and all the planking, except a thin external skin. It is also an important fact that rats very rarely make their appearance in dry places: under floors they are sometimes very destructive.

As rats will sometimes destroy the structural parts of wood framing, a few words about them may not be out of place. If poisoned wheat, arsenic, &c., be used, the creatures will simply eat the things and die under the floor, causing an intolerable stench. The best method is to make a small hole in a corner of the floor (unless they make it themselves) large enough to permit them to come up; the following course is then recommended:—Take oil of amber and ox-gall in equal parts; add to them oatmeal or flour sufficient to form a paste, which divide into little balls, and lay them in the middle of the infested apartment at night time. Surround the balls with a number of saucers filled with water—the smell of the oil is sure to attract the rats, they will greedily devour the balls, and becoming intolerably thirsty will drink till they die on the spot. They can be buried in the morning.

Building timber into new walls is often a cause of decay, as the lime and damp brickwork are active agents in producing putrefaction, particularly where the scrapings of roads are used, instead of sand, for mortar. Hence it is that bond timbers, wall plates, and the ends of girders, joists, and lintels are so frequently found in a state of decay. The ends of brestsummers are sometimes cased in sheet lead, zinc, or fire-brick, as being impervious to moisture. The old builders used to bed the ends of girders and joists in loam instead of mortar, as directed in the Act of Parliament, 19 Car. II. c. 3, for rebuilding the City of London.

In Norway, all posts in contact with the earth are carefully wrapped round with flakes of birch bark for a few inches above and below the ground.

Timber that is to lie in mortar—as, for instance, the ends of joists, door sills and frames of doors and windows, and the ends of girders—if pargeted over with hot pitch, will, it is said, be preserved from the effects of the lime. In taking down, some years since, in France, some portion of the ancient Château of the Roque d’Oudres, it was found that the extremities of the oak girders were perfectly preserved, although these timbers were supposed to have been in their places for upwards of 600 years. The whole of these extremities buried in the walls were completely wrapped round with plates of cork. When demolishing an ancient Benedictine church at Bayonne, it was found that the whole of the fir girders were entirely worm eaten and rotten, with the exception, however, of the bearings, which, as in the case just mentioned, were also completely wrapped round with plates of cork. These facts deserve consideration.

If any of our professional readers should wish to try cork for the ends of girders, they will do well to choose the Spanish cork, which is the best.

In this place it may not be amiss to point out the dangerous consequences of building walls so that their principal support depends on timber. The usual method of putting bond timber into walls is to lay it next the inside; this bond often decays, and, of course, leaves the walls resting only upon the external course or courses of brick; and fractures, bulges, or absolute failures are the natural consequences. This evil is in some degree avoided by placing the bond in the middle of the wall, so that there is brickwork on each side, and by not putting continued bond for nailing the battens to. We object to placing bond in the middle of a wall: the best way, where it can be managed, is to corbel out the wall, resting the ends of the joists on the top course of bricks; thus doing away with the wood-plate. In London, wood bond is prohibited by Act of Parliament, and hoop-iron bond (well tarred and sanded) is now generally used. The following is an instance of the bad effects of placing wood bond in walls: In taking down portions of the audience part and the whole of the corridors of the original main walls of Covent Garden Theatre, London, in 1847, which had only been built about thirty-five years, the wood horizontal bond timbers, although externally appearing in good condition, were found, on a close examination by Mr. Albano, much affected by shrinkage, and the majority of them quite rotten in the centre, consequently the whole of them were ordered to be taken out in short lengths, and the space to be filled in with brickwork and cement.

Some years since we had a great deal to do with “Fire Surveys;” that is to say, surveying buildings to estimate the cost of reinstating them after being destroyed by fire; and we often noticed that the wood bond, being rotten, was seriously charred by the fire, and had to be cut out in short lengths, and brickwork in cement “pinned in” in its place. Brestsummers and story posts are rarely sufficiently burnt to affect the stability of the front wall of a shop building.

In bad foundations, it used to be common, before concrete came into vogue, to lie planks to build upon. Unless these planks were absolutely wet, they were certain to rot in such situations, and the walls settled; and most likely irregularly, rending the building to pieces. Instances of such kind of failure frequently occur. It was found necessary, a few years since, to underpin three of the large houses in Grosvenor Place, London, at an immense expense. In one of these houses the floors were not less than three inches out of level, the planking had been seven inches thick, and most of it was completely rotten: it was of yellow fir. A like accident happened to Norfolk House, St. James’s Square, London, where oak planking had been used.

As an example of the danger of trusting to timber in supporting heavy stone or brickwork, the failure of the curb of the brick dome of the church of St. Mark, at Venice, may be cited. This dome was built upon a curb of larch timber, put together in thicknesses, with the joints crossed, and was intended to resist the tendency which a dome has to spread outwards at the base. In 1729, a large crack and several smaller ones were observed in the dome. On examination, the wooden curb was found to be in a completely rotten state, and it was necessary to raise a scaffold from the bottom to secure the dome from ruin. After it was secured from falling, the wooden curb was removed, and a course of stone, with a strong band of iron, was put in its place.

It is said that another and very important source of destruction is the applying end to end of two different kinds of wood: oak to fir, oak to teak or lignum vitæ; the harder of the two will decay at the point of juncture.

The bad effects resulting from damp walls are still further increased by hasty finishing. To enclose with plastering and joiners’ work the walls and timbers of a building while they are in a damp state is the most certain means of causing the building to fall into a premature state of decay.

Mr. George Baker, builder of the National Gallery, London, remarked, in 1835, “I have seen the dry rot all over Baltic timber in three years, in consequence of putting it in contact with moist brickwork; the rot was caused by the badness of the mortar, it was so long drying.”

Slating the external surface of a wall, to keep out the rain or damp, is sometimes adopted: a high wall (nearly facing the south-west) of a house near the north-west corner of Blackfriars Bridge, London, has been recently slated from top to bottom, to keep out damp.

However well timber may be seasoned, if it be employed in a damp situation, decay is the certain consequence; therefore it is most desirable that the neighbourhood of buildings should be well drained, which would not only prevent rot, but also increase materially the comfort of those who reside in them. The drains should be made water-tight wherever they come near to the walls; as walls, particularly brick walls, draw up moisture to a very considerable height: very strict supervision should be placed over workmen while the drains of a building are being laid. Earth should never be suffered to rest against walls, and the sunk stories of buildings should always be surrounded by an open area, so that the walls may not absorb moisture from the earth: even open areas require to be properly built. We will quote a case to explain our meaning. A house was erected about eighteen months ago, in the south-east part of London, on sloping ground. Excavations were made for the basement floor, and a dry area, “brick thick, in cement,” was built at the back and side of the house, the top of the area wall being covered with a stone coping; we do not know whether the bottom of the area was drained. On the top of the coping was placed mould, forming one of the garden beds for flowers. Where the mould rested against the walls, damp entered. The area walls should have been built, in the first instance, above the level of the garden-ground—which has since been done—otherwise, in course of time, the ends of the next floor joists would have become attacked by dry rot.

Some people imagine that if damp is in a wall the best way to get rid of it is to seal it in, by plastering the inside and stuccoing the outside of the wall; this is a great mistake; damp will rise higher and higher, until it finds an outlet; rotting in the meanwhile the wood bond and ends of all the joists. We were asked recently to advise in a curious case of this kind at a house in Croydon. On wet days the wall (stucco, outside; plaster, inside) was perfectly wet: bands of soft red bricks in wall, at intervals, were the culprits. To prevent moisture rising from the foundations, some substance that will not allow it to pass should be used at a course or two above the footings of the walls, but it should be below the level of the lowest joists. “Taylor’s damp course” bricks are good, providing the air-passages in them are kept free for air to pass through: they are allowed sometimes to get choked up with dirt. Sheets of lead or copper have been used for that purpose, but they are very expensive. Asphalted felt is quite as good; no damp can pass through it. Care must, however, be taken in using it if only one wall, say a party wall, has to be built. To lay two or three courses of slates, bedded in cement, is a good method, providing the slates “break joint,” and are well bedded in the cement. Workmen require watching while this is being done, because if any opening be left for damp to rise, it will undoubtedly do so. A better method is to build brickwork a few courses in height with Portland cement instead of common mortar, and upon the upper course to lay a bed of cement of about one inch in thickness; or a layer of asphalte (providing the walls are all carried up to the same level before the asphalte is applied hot). As moisture does not penetrate these substances, they are excellent materials for keeping out wet; and it can easily be seen if the mineral asphalte has been properly applied. To keep out the damp from basement floors, lay down cement concrete 6 inches thick, and on the top, asphalte 1 inch thick, and then lay the sleepers and joists above; or bed the floor boards on the asphalte.

The walls and principal timbers of a building should always be left for some time to dry after it is covered in. This drying is of the greatest benefit to the work, particularly the drying of the walls; and it also allows time for the timbers to get settled to their proper bearings, which prevents after-settlements and cracks in the finished plastering. It is sometimes said that it is useful because it allows the timber more time to season; but when the carpenter considers that it is from the ends of the timber that much of its moisture evaporates, he will see the impropriety of leaving it to season after it is framed, and also the cause of framed timbers of unseasoned wood failing at the joints sooner than in any other place. No parts of timber require the perfect extraction of the sap so much as those that are to be joined.

When the plastering is finished, a considerable time should be allowed for the work to get dry again before the skirtings, the floors, and other joiners’ work be fixed. Drying will be much accelerated by a free admission of air, particularly in favourable weather. When a building is thoroughly dried at first, openings for the admission of fresh air are not necessary when the precautions against any new accessions of moisture have been effectual. Indeed, such openings only afford harbour for vermin: unfortunately, however, buildings are so rarely dried when first built, that air-bricks, &c., in the floors are very necessary, and if the timbers were so dried as to be free from water (which could be done by an artificial process), the wood would only be fit for joinery purposes. Few of our readers would imagine that water forms ⅕th part of wood. Here is a table (compiled from ‘Box on Heat,’ and Péclet’s great work ‘Traité de la Chaleur’):—

Wood.

Elements.	Ordinary state.
Carbon	·408
Hydrogen	·042
Oxygen	·334
Water	·200
Ashes	·016
	1·000

Many houses at our seaport towns are erected with mortar, having sea-sand in its composition, and then dry rot makes its appearance. If no other sand can be obtained, the best way is to have it washed at least three times (the contractor being under strict supervision, and subject to heavy penalties for evasion). After each washing it should be left exposed to the action of the sun, wind, and rain: the sand should also be frequently turned over, so that the whole of it may in turn be exposed; even then it tastes saltish, after the third operation. A friend of ours has a house at Worthing, which was erected a few years since with sea-sand mortar, and on a wet day there is always a dampness hanging about the house—every third year the staircase walls have to be repapered: it “bags” from the walls.

In floors next the ground we cannot easily prevent the access of damp, but this should be guarded against as far as possible. All mould should be carefully removed, and, if the situation admits of it, a considerable thickness of dry materials, such as brickbats, dry ashes, broken glass, clean pebbles, concrete, or the refuse of vitriol-works; but no lime (unless unslaked) should be laid under the floor, and over these a coat of smiths’ ashes, or of pyrites, where they can be procured. The timber for the joists should be well seasoned; and it is advisable to cut off all connection between wooden ground floors and the rest of the woodwork of the building. A flue carried up in the wall next the kitchen chimney, commencing under the floor, and terminating at the top of the wall, and covered to prevent the rain entering, would take away the damp under a kitchen floor. In Hamburg it is a common practice to apply mineral asphalte to the basement floors of houses to prevent capillary attraction; and in the towns of the north of France, gas-tar has become of very general use to protect the basement of the houses from the effects of the external damp.

Many houses in the suburbs (particularly Stucconia) of London are erected by speculating builders. As soon as the carcase of a house is finished (perhaps before) the builder is unable to proceed, for want of money, and the carcase is allowed to stand unfinished for months. Showers of rain saturate the previously unseasoned timbers, and pools of water collect on the basement ground, into which they gradually, but surely, soak. Eventually the houses are finished (probably by half a dozen different tradesmen, employed by a mortgagee); bits of wood, rotten sawdust, shavings, &c., being left under the basement floor. The house when finished, having pretty (!) paper on the walls, plate-glass in the window-sashes, and a bran new brick and stucco portico to the front door, is quickly let. Dry rot soon appears, accompanied with its companions, the many-coloured fungi; and when their presence should be known from their smell, the anxious wife probably exclaims to her husband, “My dear! there is a very strange smell which appears to come from the children’s playroom: had you not better send for Mr. Wideawake, the builder, for I am sure there is something the matter with the drains.” Defective ventilation, dry rot, green water thrown down sinks, &c., do not cause smells, it’s the drains, of course!

There is another cause which affects all wood most materially, which is the application of paint, tar, or pitch before the wood has been thoroughly dried. The nature of these bodies prevents all evaporation; and the result of this is that the centre of the wood is transformed into touchwood. On the other hand, the doors, pews, and carved work of many old churches have never been painted, and yet they are often found to be perfectly sound, after having existed more than a century. In Chester, Exeter, and other old cities, where much timber was formerly used, even for the external parts of buildings, it appears to be sound and perfect, though black with age, and has never been painted.

Mr. Semple, in his treatise on ‘Building in Water,’ mentions an instance of some field-gates made of home fir, part of which, being near the mansion, were painted; while the rest, being in distant parts of the grounds, were not painted. Those which were painted soon became quite rotten, but the others, which were not painted, continued sound.

Another cause of dry rot, which is sometimes found in suburban and country houses, is the presence of large trees near the house. We are acquainted with the following remarkable instance:—At the northern end of Kilburn, London, stands Stanmore Cottage, erected a great many years ago: about fifty feet in front of it is an old elm-tree. The owner, a few years since, noticed cracks round the portico of the house; these cracks gradually increased in size, and other cracks appeared in the window arches, and in different parts of the external and internal walls. The owner became alarmed, and sent for an experienced builder, who advised underpinning the walls. Workmen immediately commenced to remove the ground from the foundations, and it was then found that the foundations, as well as the joists, were honeycombed by the roots of the elm-tree, which were growing alongside the joists, the whole being surrounded by large masses of white and yellow dry-rot fungus.

The insufficient use of tarpaulins is another frequent cause of dry rot. A London architect had (a few years since) to superintend the erection of a church in the south-west part of London; an experienced builder was employed. The materials were of the best description and quality. When the walls were sufficiently advanced to receive the roof, rain set in; as the clown in one of Shakespeare’s plays observed, “the rain, it raineth every day;” it was so, we are told, in this case for some days. The roof when finished was ceiled below with a plaster ceiling; and above (not with “dry oakum without pitch” but) with slates. A few months afterwards some of the slates had to be reinstated, in consequence of a heavy storm, and it was then discovered that nearly all the timbers of the roof were affected by dry rot. This was an air-tight roof.

In situations favourable to rot, painting prevents every degree of exhalation, depriving at the same time the wood of the influence of the air, and the moisture runs through it, and insidiously destroys the wood. Most surveyors know that moist oak cills to window frames will soon rot, and the painting is frequently renewed; a few taps with a two-feet brass rule joint on the top and front of cill will soon prove their condition. Wood should be a year or more before it is painted; or, better still, never painted at all. Artificers can tell by the sound of any substance whether it be healthy or decayed as accurately as a musician can distinguish his notes: thus, a bricklayer strikes the wall with his crow, and a carpenter a piece of timber with his hammer. The Austrians used formerly to try the goodness of the timber for ship-building by the following method: One person applies his ear to the centre of one end of the timber, while another, with a key, hits the other end with a gentle stroke. If the wood be sound and good, the stroke will be distinctly heard at the other end, though the timber should be fifty feet or more in length. Timber affected with rot yields a particular sound when struck, but if it were painted, and the distemper had made much progress, with no severe stroke the outside breaks like a shell. The auger is a very useful instrument for testing wood; the wood or sawdust it brings out can be judged by its smell; which may be the fresh smell of pure wood: the vinous smell, or first degree of fermentation, which is alcoholic; or the second degree, which is putrid. The sawdust may also be tested by rubbing it between the fingers.

According to Colonel Berrien, the Michigan Central Railroad Bridge, at Niles, was painted before seasoning, with “Ohio fire-proof paint,” forming a glazed surface. After five years it was so rotten as to require rebuilding.

Painted floor-cloths are very injurious to wooden floors, and frequently produce rottenness in the floors that are covered with them, as the painted cloth prevents the access of air, and retains whatever dampness the boards may absorb, and therefore soon causes decay. Carpets are not so injurious, but still assist in retarding free evaporation.

Captain E. M. Shaw, in ‘Fire Surveys,’ thus writes of the floors of a building, “They might with advantage be caulked like a ship’s deck, only with dry oakum, without pitch.” Let us see how far oil floor-cloth and kamptulicon will assist us in obtaining an air-tight floor.

In London houses there is generally one room on the basement floor which is carefully covered over with an oiled floor-cloth. In such a room the dry rot often makes its appearance. The wood absorbs the aqueous vapour which the oil-cloth will not allow to escape; and being assisted by the heat of the air in such apartments, the decay goes on rapidly. Sometimes, however, the dry rot is only confined to the top of the floor. At No. 106, Fenchurch Street, London, a wood floor was washed (a few years since) for a tenant, and oil-cloth was laid down. Circumstances necessitated his removal a few months afterwards; and it was then found that the oil-cloth had grown, so to speak, to the wood flooring, and had to be taken off with a chisel: the dry rot had been engendered merely on the surface of the floor boards, as they were sound below as well as the joists: air bricks were in the front wall.

We have seen many instances of dry rot in passages, where oiled floor-cloth has been nailed down and not been disturbed for two or three years.

In ordinary houses, where floor-cloth is laid down in the front kitchen, no ventilation under the floors, and a fire burning every day in the stove, dry rot often appears. In the back kitchen, where there is no floor-cloth, and only an occasional fire, it rarely appears. The air is warm and stagnant under one floor, and cold and stagnant under the other: at the temperature of 32° to 40° the progress of dry rot is very slow.

And how does kamptulicon behave itself? The following instances of the rapid progress of dry rot from external circumstances have recently been communicated to us; they show that, under favourable circumstances as to choice of timber and seasoning, this fungus growth can be readily produced by casing-in the timber with substances impervious, or nearly so, to air.

At No. 29, Mincing Lane, London, in two out of three rooms on the first floor, upon a fire-proof floor constructed on the Fox and Barrett principle (of iron joists and concrete with yellow pine sleepers, on strips of wood bedded in cement, to which were nailed the yellow pine floor-boards) kamptulicon was nailed down by the tenant’s orders. In less than nine months the whole of the wood sleepers, and strips of wood, as well as the boards, were seriously injured by dry rot; whilst the third room floor, which had been covered with a carpet, was perfectly sound.

At No. 79, Gracechurch Street, London, a room on the second floor was inhabited, as soon as finished, by a tenant who had kamptulicon laid down. This floor was formed in the ordinary way, with the usual sound boarding of strips of wood, and concrete two inches thick filled in on the same, leaving a space of about two inches under the floor boards. The floor was seriously decayed by dry rot in a few months down to the level of the concrete pugging, below which it remained sound, and could be pulled up with the hand.

We will now leave oil-cloth and kamptulicon, and try what “Keene’s cement” will do for an “air-tight” partition of a house.

At No. 16, Mark Lane, London, a partition was constructed of sound yellow deal quarters, covered externally with “Keene’s cement, on lath, both sides.” It was removed about two years after its construction, when it was found that the timber was completely perished from dry rot; so much so, that the timbers parted in the middle in places, and were for some time afterwards moist.

It is still unfortunately the custom to keep up the old absurd fashion of disguising woods, instead of revealing their natural beauties. Instead of wasting time in perfect imitations of scarce or dear woods, it would be much better to employ the same amount of time in fully developing the natural characteristics of many of our native woods, now destined for decorative purposes because they are cheap and common; although many of our very commonest woods are very beautifully grained, but their excellences for ornamentation are lost because our decorators have not studied the best mode of developing their beauties. Who would wish that stained deal should be painted in imitation of oak? or that the other materials of a less costly and inferior order should have been painted over instead of their natural faces being exposed to view? There are beauties in all the materials used. The inferior serve to set off by comparison the more costly, and increase their effect. The red, yellow, and white veins of the pine timber are beautiful: the shavings are like silk ribbons, which only nature could vein after that fashion, and to imitate which would puzzle all the tapissiers of the Rue Mouffetard, in Paris.

Why should not light and dark woods be commonly used in combination with each other in our joinery? Wood may be stained of various shades, from light to dark. The dirt or dust does not show more on stained wood than it does on paint, and can be as easily cleaned and refreshed by periodical coats of varnish. Those parts subjected to constant wear and tear can be protected by more durable materials, such as finger-plates, &c. Oak can be stained dark, almost black, by means of bichromate of potash diluted with water. Wash the wood over with a solution of gallic acid of any required strength, and allow it to thoroughly dry. To complete the process, wash with a solution of iron in the form of “tincture of steel,” or a decoction of vinegar and iron filings, and a deep and good stain will be the result. If a positive black is required, wash the wood over with gallic acid and water two or three times, allowing it to dry between every coat; the staining with the iron solution may be repeated. Raw linseed oil will stay the darker process at any stage.

Doors made up of light deal, and varied in the staining, would look as well as the ordinary graining. Good and well-seasoned materials would have to be used, and the joiners’ work well fitted and constructed. Mouldings of a superior character, and in some cases gilt, might be used in the panels, &c. For doors, plain oak should be used for the stiles and rails, and pollard oak for the panels. If rose-wood or satin-wood be used, the straight-grained wood is the best adapted for stiles and rails; and for mahogany doors, the lights and shades in the panels should be stronger than in the stiles and rails.

Dark and durable woods might be used in parts most exposed to wear and tear.

Treads of stairs might be framed with oak nosings, if not at first, at least when necessary to repair the nosings.

Skirtings could be varied by using dark and hard woods for the lower part or plinth, lighter wood above, and finished with superior mouldings. It must, however, be remembered that, contrary to the rule that holds good with regard to most substances, the colours of the generality of woods become considerably darker by exposure to the light; allowance would therefore have to be made for this. All the woodwork must, previously to being fixed, be well seasoned.

The practice here recommended would be more expensive than the common method of painting, but in many cases it would be better than graining, and cheaper in the long run. Oak wainscot and Honduras mahogany doors are twice the price of deal doors; Spanish mahogany three times the price. When we consider that by using the natural woods, French polished, we save the cost of four coats of paint and graining (the customary modes), the difference in price is very small. An extra 50l. laid out on a 500l. house would give some rooms varnished and rubbed fittings, without paint. Would it not be worth the outlay? It may be said that spots of grease and stains would soon disfigure the bare wood; if so, they could easily be removed by the following process: Take a quarter of a pound of fuller’s earth, and a quarter of a pound of pearlash, and boil them in a quart of soft water, and, while hot, lay the composition on the greased parts, allowing it to remain on them for ten or twelve hours; after which it may be washed off with fine sand and water. If a floor be much spotted with grease, it should be completely washed over with this mixture, and allowed to remain for twenty-four hours before it is removed.

Let us consider how we paint our doors, cupboards, &c., at the present time. For our best houses, the stiles of our doors are painted French white; and the panels, pink, or salmon colour! For cheaper houses, the doors, cupboards, window linings, &c., are generally two shades of what is called “stone colour” (as if stone was always the same colour), and badly executed into the bargain: the best rooms having the woodwork grained in imitation of oak, or satin-wood, &c. And such imitations! Mahogany and oak are now even imitated on leather and paper-hangings. Wood, well and cleanly varnished, stained, or, better still, French polished, must surely look better than these daubs. But French polish is not extensively used in England: it is confined to cabinet pieces and furniture, except in the houses of the aristocracy. Clean, colourless varnish ought to be more generally used to finish off our woodwork, instead of the painting now so common. The varnish should be clean and colourless, as the yellow colour of the ordinary varnishes greatly interferes with the tints of the light woods.

In the Imperial Palace, at Berlin, one or two of the Emperor’s private rooms are entirely fitted up with deal fittings; doors, windows, shutters, and everything else of fir-wood. “Common deal,” if well selected, is beautiful, cheap, and pleasing.

We have seen the offices of Herr Krauss (architect to Prince and Princess Louis of Hesse), who resides at Mayence, and they are fitted up, or rather the walls and ceilings are lined, with picked pitch pine-wood, parts being carved, and the whole French polished, and the effect is much superior to any paint, be it “stone colour,” “salmon colour,” or even “French white.”

The reception-room, where the Emperor of Germany usually transacts business with his ministers, and receives deputations, &c., as well as the adjoining cabinets, are fitted with deal, not grained and painted, but well French polished. The wood is, of course, carefully selected, carefully wrought, and excellently French polished, which is the great secret of the business. In France, it is a very common practice to polish and wax floors.

The late Sir Anthony Carlisle had the interior woodwork of his house, in Langham Place, London, varnished throughout, and the effect of the varnished deal was very like satin-wood.

About forty years since, Mr. J. G. Crace, when engaged on the decoration of the Duke of Hamilton’s house, in the Isle of Arran, found the woodwork of red pine so free from knots, and so well executed, that instead of painting it, he had it only varnished. It was a great success, and ten years after looked nearly as well as when first done.

The late Mr. Owen Jones, whose works on colour decoration are well known, was employed a few years since by Mr. Alfred Morrisson to decorate his town and country houses. At the country house (Fonthill House), Mr. Jones built a room for the display of Chinese egg-shell pottery, the chimneypiece and fittings being entirely of ebony, inlaid with ivory, and the ceiling of wood, panelled and inlaid, the mouldings being black and gold. At the town house, in Carlton House Terrace, London, the woodwork of the panelling, dadoes, doors, architraves, window-shutters, and all the rooms on the ground and first floors is inlaid, from designs by Mr. Jones, with various woods of different kinds, the colours of which were carefully selected by him, with a view to perfect harmony of colouring.

A house has recently been erected (from the designs of Mr. J. W. McLaughlin, architect) near Cincinnati, Ohio, United States, which is a perfect model with regard to the amount of woodwork used. The walls of the hall are finished with walnut wainscoting; the fireplace is an open one, with a walnut mantelpiece, surmounted by three statues, Peace, Plenty, and Harmony, supporting the carved wooden cornice. The Elizabethan staircase has carved panels of maple. The library is wainscoted to the ceiling in black walnut, inlaid with ebony. The dining room is also wainscoted in the richest style in oak, with polished mahogany panels. The floors are of marquetry, of different woods and patterns. The chamber story is finished in oak and walnut, with mahogany in the panels. The entire interior finish of the house is of hard wood, varnished and rubbed in cabinet style. This is as it should be for a gentleman’s residence.

We believe the largest house now being erected in London is from the designs of Mr. Knowles, jun., for Baron Albert Grant, at Kensington. We have not seen it, but we hope it will be finished in the Cincinnati style, as far as regards the amount of ornamental woods used.

There is a cynical French proverb, which says, “When we cannot have what we love, we must love what we have.” But surely this cynical proverb cannot be applied to “stone colour” paint on wood. The Japanese, however, some years since, determined not to follow this advice, for when the English Government, at Admiral Sterling’s suggestion, sent to the Tycoon a very fine steam vessel, the Japanese (who abhor paint about their ships) immediately commenced to scrub off the paint. According to Sir Rutherford Alcock, they have been steadily engaged in scrubbing it off ever since the boat has come into their possession, and by dint of labour and perseverance have nearly succeeded. All the fine imitation satin-wood and the gilt work have been reduced to a very forlorn state. The Japanese not only decline to follow advice, but they are a very difficult race of people from whom to obtain correct information. When Mr. Veitch was at Yeddo, on a visit to the Legation, in quest of botanical specimens, he saw a pine-tree from which he desired a few seeds. “Oh,” said the inevitable yaconins, “those trees have no seed!”—“But there they are,” replied the unreasonable botanist, pointing to some. “Ah, yes, true; but they will not grow,” was the reply.

If we must take our fashions from royalty and the aristocracy, and if we must go abroad for them, surely the above examples will suffice; but if we must have paint, then the preservative solution, now being extensively used in the restoration and renovation of St. Paul’s Cathedral, under the superintendence of Mr. F. C. Penrose, the architect to the Dean and Chapter, appears to possess several good qualities. The preservative solution, which is manufactured by the Indestructible Paint Company, is said to be as follows: 1st, that it is colourless and invisible; 2nd, in no way does it alter the appearance of the surface; 3rd, it prevents the growth of vegetation; and 4th, that it resists the action of the atmosphere and changes of weather, not only preventing but also arresting decay.

It is necessary that the wood selected (if not to be painted) should be well grown, and from a fully developed tree, where all the fibres or grain are distinctly marked. The beauty of the wood, when properly treated, consists in the brilliant manner in which the rich, deep yellow streaks or layers of the hard wood are developed under the hands of the skilful polisher. These yellow veins show through the polish like clear and beautifully marked streaks of amber; and strongly reflecting the light, they produce a very pleasing effect. The yellow, variegated, hard part of the wood forms a very excellent contrast to the delicate whiteness of the softer parts of the board; and, if skilfully selected, the effect will be much admired, and certainly preferred to the best imitation of the more rare and expensive woods. In arranging doors, panels, &c., much will, of course, depend in selecting the wood, in placing the best parts in the panels, so that when polished the most pleasing effects will be produced. Much, too, depends on skilful workmanship and smooth finish, which can only be obtained by care, and using well-seasoned wood; but this is the case with all species of wood.

Should any young architect, after reading the preceding remarks, be desirous of employing natural woods in his building works, we advise him, before he attempts this kind of colour decoration, to study Mr. Owen Jones’ lecture on “Colour in the Decorative Arts,” delivered before the Society of Arts, 1852; and likewise M. Chevreul’s ‘Laws of the Simultaneous Contrast of Colours’; we also recommend him to—

Use moderate things elegantly, and elegant things moderately.

Oak, walnut, maple, elm, and some other woods become of very dark colour, but can be made to receive a fine polish, and could often be employed for panels with good effect. In some cases there is great contrast of tint in the same log after preparation, so that these might be inapplicable except in smaller pieces, or perhaps by applying the process after the work has been made; but sycamore, beech, and some other woods are generally uniform, except as regards the previous grain of the wood.

As to the matter of showing the end of the grain, according to the Gothic principle the beauty of a wood consists in showing the end of the grain; but, at the same time, the classic principle is that there is a greater beauty in the side way of the grain than in the end way.

Although varnish and polish both form a glazing, and give a lustre to the wood they cover, as well as heighten the colours of the wood, yet from their want of consistence they are liable to yield to any shrinking or swelling, rising in scales or cracking, when much knocked about. Waxing, on the contrary, resists percussion, but it does not possess in the same degree as varnish the property of giving lustre to the bodies on which it is applied; any accidents, however, to its polish are easily repaired by rubbing.

The woodwork of the Swiss Cottage, at the late Colosseum, London, in the Regent’s Park, was only varnished.

In using stain on any description of wood, the stain should always be allowed to get quite dry before sizing, as that gives it a fair chance of striking into the wood. Glue size is the best for stained work, made so thin that there is no fear of putting it on in patches. After the size is quite dry also, varnish; and if the first coat does not stand out quite sufficiently to please the eye, give it a second coat. Some persons use stain and varnish together, doing away with size; but this is a very poor method, for should the wood get scratched or damaged in any way, the varnish and stain come off together, leaving a white place, if it be white wood that is stained. A painter who has been in the trade forty years, recently remarked to us, “You must size, or else the varnish won’t come out; it won’t show that it is varnish; the wood soaks it up; while there is any suction going on the varnish’ll go in. The sizing stops all suction.”

A great many experiments and attempts have been made at different times to colour wood. John of Verona first conceived the idea. The celebrated B. Pallissy investigated the cause of the veins, &c., in wood, and tried mordant solutions applied to the surface, wetting the surface with certain acids, immersing the wood in water to bring out the veinage, &c.

Ebony has often been imitated by penetrating sycamore, plane, and lime woods to a certain depth with pyrolignite of iron, gall-nuts, &c.

Werner, in 1812, obtained great success at Dijon in colouring the woods by filtration. Marloye, in 1833, constructed a machine to colour wood by placing it erect in a cylinder, sucking out the air at one end, and forcing up the colouring solution through the other. He gave the credit of this to Bréant. Marloye has manufactured many mathematical instruments of wood coloured in this way, which does not warp.

If we could afford the space, we would willingly give a résumé of the attempts of well known experimentalists to colour wood. We can only give the year and name in each case:

• 1709. Magnol.
• 1733. La Baisse.
• 1735. Hales.
• 1735. Buffon.
• 1754. Bonnet.
• 1758. Du Hamel.
• 1804. Saussure.

During the recent war between France and Germany, the latter country advanced matters, their supplies of coloured woods from France being gone.

As we have made so many remarks against painting wood, it is only right that we should give some description of it, which we will now do.

House painting, according to Mr. W. Papworth, in his lecture on “Fir, Deal, and House Painting,” 1857, did not come into general use until about the period of William and Mary, and Anne, up to which time either colouring by distemper or by whitewash had been in vogue for plaster work, leaving inside woodwork more or less untouched.

We think, without wishing to think too loud, that house painting was invented by a bad builder, in the seventeenth century, because

Putty and paint cover a multitude of sins.

The process of graining and marbling may be traced back as far at least as the time of James III. of Scotland (1567-1603), during whose reign a room of Hopetown Tower was painted in imitation of marble. Before that period, imitations were done in “stone” colour, “marble” colour, wainscot colour, &c. In 1676, marbling was executed as well as imitations of olive and walnut woods; and in 1688 tortoise-shell was copied on battens and mouldings. Mahogany was imitated in 1815, and maple wood in 1817. But why imitate mahogany, when the grain of the wood differs so much in texture, and in the appearance of the different and beautiful shades, technically termed roe, broken roe, bold roe, mottle, faint mottle, and dapple.

The following description will give the reader some idea of ordinary painting. The woodwork having been prepared for fixing, has first to undergo the process of “knotting,” in order to prevent the turpentine in the knots of fir-wood from passing through the several coats of paint. One method for best work is to cut out the knot whilst the work is at the bench to a slight depth, and to fill up the hole with a stiff putty made of white lead, japan, and turpentine. There are many ways of killing the knots: the best and surest is to cover them with gold or silver leaf. Sometimes a lump of fresh slaked lime is laid on for about twenty-four hours, then scraped off, a coating of “size knotting” applied, and if not sufficiently killed, they are coated with red and white lead in linseed oil, and rubbed down when dry. The general method is to cover the parts with size knotting, which is a preparation of red lead, white lead, and whitening, made into a thin paste with size. The most common mode is to paint them with red ochre, which is worth nothing. The next process is that of priming, which consists in giving a coat of white and red lead, and a little dryers in linseed oil. This is the first coat, and upon which the look of the paint on completion depends. This first, or priming coat, is put on before “stopping” the work, should that process be required. It consists in filling up with putty any cracks or other imperfections on the surface of the wood. If the putty used in the process of stopping be introduced before the first coat of colour is laid on, it becomes loose when dry. After this first coat, pumicing is resorted to for removing all irregularities from the surface. It is worth recollecting that old white lead is much superior to new for all painting operations. A smooth surface being thus obtained, the second coat is given, consisting of white lead and oil: about one-fourth part of turpentine is sometimes added for quick work. If four coats are to be laid on, this second one has sometimes a proportion of red lead, amounting to a flesh colour; but if only three, it is generally made to assume the tint of the finishing coat. It should have a good body, and be laid even. This coat, when thoroughly dry and hard, is, in best work, rubbed down with fine sand paper, and then the third coat, or “ground colour,” applied of a somewhat darker tint than wanted when finished, having sufficient oil for easy working, but not too fluid: thus two-thirds oil, and one-third turpentine. The “flatting” coat follows, the object of which is to prevent the gloss or glaze of the oil, and to obtain a flat, dead appearance. White lead is mixed with turpentine, to which a little copal is sometimes added, and when the tint is put in it is always made lighter than the ground colour, or it would, when finished, appear in a series of shades and stripes. Flatting must be executed quickly, and the brush is generally, if not always, carried up the work, and not across it.

To clean paint, raw alkalies should not be used, as they will infallibly take off the flatting coat. The best mode of cleaning is by means of good soap, not too strong, laid on with a large brush, so as to make a lather: this should be washed off clean with a sponge, and wiped dry with a leather.

We must draw to a conclusion.

One cause of the decay of modern buildings, and frequent cases of dry rot, is owing to the employment of bad builders. We advise the non-professional reader to employ an architect or surveyor when he desires to speculate in bricks and mortar: it is the cheapest course. If he doubts the truth of what we have written, we can assure him he will be a mere child in the hands of a bad or scamping builder; that is to say, he will obtain a badly-erected house,—a cheap contract, and a long bill of extras.

There are seven classes of bad builders—1st, the bad builder who does not know his business; 2nd, the bad builder who has no money to carry it on with; 3rd, the partial scamp; 4th, the regular scamp; 5th, the thorough scamp; 6th, the “jerry” builder; and 7th, the vagabond. There is an instance of the latter class given by Mr. Menzies in his fine work on ‘Windsor Park,’ 1864. We could give examples of all these classes, and draw the line between each class, impossible as it may seem: they are always looking out for customers, without architects.

We could assist the non-professional reader by quoting the advice given by several architects (viz. Sir C. Wren, C. Barry, B. Smirke, W. Chambers, and W. Tite) relative to buildings, but there is a Danish proverb which, translated into English, runs as follows: “He who builds according to every man’s advice will have a crooked house.”

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CHAPTER VII.
ON THE PRESERVATION OF WOODEN BRIDGES, JETTIES, PILES, HARBOUR WORKS, ETC., FROM THE RAVAGES OF THE TEREDO NAVALIS AND OTHER SEA-WORMS.

“Perforated sore

And drilled in holes, the solid oak is found

By worms voracious, eaten through and through.”

Sir John Barrow.

As the destruction of timber by fungi has been called the vegetable rot, it may not be inappropriate to term the destruction of wood by various worms and insects, the animal rot.

We have four natural enemies to deal with: 1st, the dry rot, that attacks our houses, &c.; 2nd, the worms, or boring animals, which destroy our ships and harbours; 3rd, the rust, that eats our iron; and 4th, the moisture and gases, that destroy our stone.

There are three classes of destructive insects which prey upon timber trees, founded upon the manner in which they carry on their operations—viz. those which feed upon the leaves and tender shoots; those which feed upon the bark and the albumen; and those which feed upon the heart-wood.

It is to be observed that some of the insects which feed upon the heart of wood do not cease their ravages upon the removal of the tree; but that, on the contrary, the Cossus syrex, of our indigenous fauna, and the larvæ of the Callidium bajutum, which are often found in imported timber, continue to devour the wood long after it has been inserted in buildings. There seem to be very few means of defence against this class of destructive agents; and very few trustworthy indications of their existence, or of the extent of the ravages they have committed, are to be discovered externally; and it thus frequently happens that a sound, hearty-looking stick of timber may be so seriously bored by these insects as to be of comparatively little value for building purposes of any description. The soft and tender woods, and such as are of a saccharine nature in their juices, are the most liable to be assailed by worms; those which are bitter are generally, if not invariably, exempt; it is obvious, therefore, that those palatable juices, which are so conducive to their production and propagation, should be got rid of by thorough seasoning, and, if further precaution be necessary, that the infusion of some bitter decoction into the pores of the wood will be an effectual preventive; and for which those woods that are of a regular grain afford sufficient facilities. Ash, if felled when abounding in sap, is very subject to worms; beech, under similar circumstances, is also liable to their attacks; likewise alder and birch; in these woods water seasoning is sometimes found to be a good preventive; the sapwood of oak is also thus improved; the silver fir is subject to them; the sycamore is rather so; alder is said when dry to be very susceptible of engendering them; the cedar, walnut, plane, cypress, and mahogany are examples of woods which discourage their advances. It has been stated that Robert Stevenson (not the son of the “Father of Railways”), of Edinburgh, at Bell Rock Lighthouse (of which he was engineer), between 1814 and 1843, found that greenheart wood, beef wood, and bullet tree were not perforated by the Teredo navalis, and teak but slightly so. Later experiments show that the “jarrah” of the East, also, is not attacked. Lignum vitæ is said to be exempt. The cost of these woods prevents their general use.

In 1810, Stevenson first noticed the teredo in piles, and specimens of the creatures in wood were sent to Dr. Leach, of the British Museum, in 1811, who examined them, and noticed their peculiarities. Stevenson, settled on Bell Rock during many years (like a new Robinson Crusoe), was enabled to watch the injuries done to the piles by the teredo. With piles which had been subjected to Kyan’s process before immersion, the wood was attacked at the end of the twenty-eighth month, and was entirely destroyed in the seventh month of the fifth year. With Payne’s, it lasted a year longer.

We can give the names of those who have given much time and attention to this subject. At the bottom of this page a list of works of reference[16] will be found useful. Messrs. Stevenson (engineer of Bell Rock Lighthouse), Harting (Member of the Academy of Sciences of the Pays-Bas), de Quatrafages, Deshayes, Caillaut, Hancock, Dagneau, de Gemini, Kater, Crepin (Engineer-in-Chief, of Belgium), and A. Forestier (Engineer-in-Chief of the Bridges, &c., of France).

The termite, or white ant, is the most destructive insect to timber on land, whilst the teredo reigns supreme of sea worms in the sea. The former we shall treat of in our next chapter, the latter we propose considering at some length in this.

The marine worm, of which there are accounts in all parts of the world, has been known, by its effects, for hundreds of years; indeed, Ovid spoke of it nineteen hundred years ago, and it is even mentioned by Homer. Fossil terredines of great antiquity have been found near Southend; also pieces of petrified wood from the greensand, near Lyme and Sidmouth, bored by ancient species of teredo; also from Bath, and from Doulting, near Shepton Mallet, specimens of oolite, with petrified corallines in it, pierced by boring shells.

It is said that this worm is a native of India, and that it was introduced to Holland some 200 years ago, from whence it has spread through the ports of northern Europe.

The Teredo navalis[17] is very destructive to harbour works and piling. The Southampton water is particularly infested with it; in fact, the teredo is found in every port to which coals are carried south of the Tees; in the Thames, as high up as Gravesend; and northward as far as Whitby. It is also found at Ryde, Brighton, and Dover. Traces of the ravages of the Teredo navalis, and of the Limnoria terebrans, have at various periods been found from the north of Scotland and Ireland, on almost every coast, to the Cape of Good Hope and Van Dieman’s Land, in the eastern hemisphere; and, in the western hemisphere, from the river St. Lawrence to Staten Island, near Terra del Fuego, almost in the Polar Sea; so that although this maritime scourge is rifest in warm climates, yet cold latitudes are not exempt from it.

At the Crystal Palace, Sydenham, may be seen the destructive Teredo navalis in a bottle, and there may also be seen mahogany perforated by it, and fir piles from Lowestoft Harbour, which were rendered useless by the ravages of the worm and the limnoria three years after they were driven, showing the necessity of defending timber intended for marine construction. A specimen of American oak from the dock gates of Lowestoft Harbour, which had been four years under water, and a part of a fir-pile from the dockyard creek at Sevastopol, also show the destructive powers of the teredo. At the South Kensington and British Museums, London, specimens of this worm may also be seen, as well as pieces of timber perforated by it.

The bottoms of ships, and timbers exposed to the action of the sea, are often destroyed by the teredo.

The gunboats constructed during the Crimean war suffered far more from dry rot and the teredo than the shot and shell of the Russians. One cannot even guess at the mischief perpetrated every year all along our shores, in docks and harbours, by the boring animals that penetrate all woods not specially protected. We cannot count the number of the ships that have foundered at sea, owing to those few inches of timber, on which all depended, being pierced or destroyed by the worm or fungus.

In the short space of twelve years these destructive worms were known to make such havoc in the fir piles of a bridge at Teignmouth, that the whole bridge fell suddenly, and had to be totally reconstructed.

The wooden piers of Bridlington were nearly wholly destroyed by worms; and the pile fenders on the stone piers at Scarborough were generally cut through in a few years.

At Dunkirk, wooden jetties are so speedily eaten away that they require renewal every twelve or fifteen years. At Havre, a stockade was entirely destroyed in six months. At Lorient, wood only lasts about three years in the sea-water; and at Aix, the hull of a stranded vessel was found to have lost half its weight in six months, from the ravages of these animals.

The reason why Balaclava, in Russia, is not a place of considerable mercantile importance is owing in a great measure to the destructive ravages of the worms with which its waters are infested, and by which the hulls of ships remaining there for any length of time become perforated.

The piles of the jetties in Colombo Harbour, Ceylon, which are mostly of satin-wood, and about 14 inches in diameter, are so pierced by these worms in the course of twelve months as to require renewal.

Portion of pile, from Balaclava harbour, Russia; riddled by the Teredo Navalis.

The cofferdam at Sheerness was destroyed by the teredo. After a time, it was no uncommon occurrence to see several piles, apparently sound, floated away at each tide; indeed, they were so thoroughly perforated by the teredo that in still weather, by putting the ear to the side of the pile, the worms could be heard at their boring labours.

The almost total destruction of the pier-head of the old Southend Pier in a few years, is another instance of the serious damages these worms cause. The old pier-head was erected in the year 1833, and in three years the majority of the wooden piles had been almost destroyed, and at the end of ten years, in addition to the piles being all eaten through by the worms, the whole structure had sunk 9 inches at the western end, so that in a short time it would have fallen. The materials with which the work was constructed were of good quality, the fir being Memel, and the oak of English growth; it was all perfectly sound in those places were the teredo had not attacked it, and indeed portions of it were again used in the construction of the extension of the pier. The whole of the timber work was well coated with pitch and tar previously to being fixed, but notwithstanding these precautions, and an apparent determination to protect the pier-head by copper sheathing, brushing, cleaning, and constant watchfulness, the teredo made its appearance, and committed such ravages that the entire destruction of the pier-head soon appeared inevitable. The Teredo navalis first showed itself six months after the completion of the work, and was reported within twelve months to have seriously injured the piles above the copper, whilst at about low-water mark, of neap tides, nearly all the piles exhibited appearances of destruction, the limnoria, as well as the teredo, having seriously attacked them; and in less than four years from the completion of the pier-head, they had progressed in their work to such an extent that some of the piles were entirely eaten through, both above and below the copper sheathing; in consequence of this the stability of the structure was materially injured, and, on examination, it was discovered that the ground had been considerably washed away by the action of the sea, and that the piles below the copper were exposed to the action of the teredo.

The first appearances of the Teredo navalis are somewhat singular, inasmuch as the wood which has been perforated by it presents to the casual observer no symptom of destruction on the surface, nor are the animals themselves visible, until the outer part of the wood has been broken away, when their shelly habitations come in sight, and show the perfect honeycomb they have formed; on a closer examination of the wood, however, a number of minute perforations are discovered on the surface, generally covered with a slimy matter; and on opening the wood at one of these, and tracing it, the tail of the animal is immediately found, and after various windings and turnings, the head is discovered, which, in some cases, is as much as 3 feet from the point of entrance; sometimes it will happen, especially if the wood has been much eaten, that their shelly tubes are partly visible on the surface, but this is rare; they enter at the surface, and bore in every direction, both with and against the grain of the wood, growing in size as they proceed.

The Rev. W. Wood writes, in 1863: “I have now before me a portion of the pier at Yarmouth, which is so honeycombed by this terrible creature that it can be crushed between the hands as if it were paper, and in many places the wood is not thicker than ordinary foolscap. This piece was broken off by a steamer which accidentally ran against it; and so completely is it tunnelled, that although it measures 7 inches in length and about 11 in circumference, its weight is under 4 ounces, a considerable portion of even that weight being due to the shelly tubes of the destroyers.”

The eggs of the teredo affix themselves to the wood they are washed against, are then hatched, and the worm commences boring; each individual serves by itself for the propagation of the species; and they rarely injure each other’s habitations. Any timber, constantly under water, but not exposed to the action of the air at the fall of the tide, is extremely likely to be destroyed by them. They appear to enter the wood obliquely, to take the grain of the fibre, and more generally to bore with it downwards, where the perforations are left dry at low water.

It has been stated by some authorities that the teredo is only a destructive creature, and seeks the wood as a shelter, from instinctive dread of some larger animals, but there is no doubt this insect feeds upon wood. Mr. John Paton, C.E. (to whom we are indebted for much information on these worms), in conjunction with Mr. Newport, the eminent physiologist and anatomist, on carefully dissecting this animal for the purpose of ascertaining its general character, and more particularly the nature of its food, found digested portions of wood in its body, so that there is no doubt that the teredo does feed upon the particles of the wood, and to this its rapid and extraordinary growth must be mainly attributed.

The Lyceris, which destroys the Teredo Navalis.

The Teredo Navalis, which destroys wood.

Portion of Timber pile destroyed by Sea Worms.

The Teredo navalis, or, as it is sometimes called, the Ship Worm, is one of the Acephalous mollusca, order Conchifera, and of the family of the Pholadariæ. It is of an elongated vermiform shape, the large anterior part of which constitutes the boring apparatus, and contains the organs of digestion, and the posterior, gradually diminishing in size, those of respiration. The body is covered with a transparent skin, through which the motion of the intestines and other remarkable peculiarities are plainly visible. The posterior or tail portion is armed at its extremity, with two shells, and has projecting from it a pair of tubular organs, through which the water enters, for the purpose of respiration; this portion is always in the direction of the surface, and apparently in immediate contact with the water, but does not bore. The anterior portion of the animal is that by which it penetrates the wood, being well armed for the purpose by having, on each side, a pair of strong valves, formed of two pieces, perfectly distinct from one another; the larger piece protects the sides and surface of the extremities, and has a shelly structure projecting from the interior, to which the muscles are attached; the smaller piece is more convex, and covers that part which should be regarded as the anterior surface of boring. This portion of the shell is deeply carniated, and seems to constitute the boring apparatus. The shells form an envelop around the external tegument of the animal, which even surrounds the foot, or part by which it adheres to the wood. The neck is provided with powerful muscles. The manner in which it appears to perforate the wood is by a rotary motion of the foot, carrying round the shells, and thus making those parts act as an auger, which is kept, or retained in connection with the wood, by the strong adherence of the foot. The particles of wood removed by this continued action of the foot, and the valves, are engorged by the animal, for between the junction of the two large shells there is a longitudinal fissure in the foot, which appears to be formed by a fold of this portion of the two sides, thus forming a canal to the oral orifice, and along which the particles of wood bored out, are conveyed to the mouth. The mouth, or entrance to the digestive organs, is of a funnel shape, and consists of a soft, or membraneous surface, capable of being enlarged, and leading into an œsophagus, which passes backwards towards the dorsal surface of the animal. At or near the termination of the œsophagus, there is a glandular organ, the use of which is possibly to secrete a fluid for assisting in the digestion of the wood, and not, as has been supposed, to act as a solvent; for if such were the case, it would most probably be situated at its commencement instead of at its termination. At a short distance behind this organ are two other large glandular bodies, the use of which may also be to secrete fluid for the purpose of digestion. The œsophagus terminates in a large dilatation, into which these organs pour their contents; at its posterior end the canal is dilated into a very large elongated sac, which extends backwards to about one-fourth of the length of the whole animal, and is filled with food, while from its anterior, or upper surface, it has an oval, muscular formation, from which the alimentary canal is continued forwards, and, after making a few turns, passes backwards, in an almost direct line, on the upper surface of the large sac, again passing backwards and forwards, until it finally arrives at its termination, which it passes round, and then proceeds, in a direct line, to the anal outlet. In the lower portion of the œsophagus, and also in the sac, distinct portions of woody fibre of an extremely minute character were found by the aid of the microscope of a power of three hundred, and this was the character of the whole of the contents of the alimentary canal.

The teredo lines the passage in the wood with a hard shell; this shell is formed around, but does not adhere to the body; it is secreted by the external covering, which, in its first formation, is extremely fragile, but becomes hardened by contact with the water, and adheres to the wood, from which it may, however, be easily detached. The interior of this shell is not filled by the body of the teredo, but a large space around it is occupied with water, admitted through the small orifice in the surface of the wood through which the animal first entered; the water being drawn through the respiratory tubes, into the bronchial cavity of the body, is expired again through the same orifice, and this, in conjunction with the valve-like shells attached at this part, induces a current round the animal which removes the excreted fœtal matter. The shells are very smooth on the inner surface, but are somewhat rougher on the exterior; they are much harder and firmer in the cells of the older animals than in the young ones, and are composed of several annular parts, differing greatly in their length.

It is no less curious than wonderful to observe the mysterious instinct which apparently regulates the mechanical skill of the teredo, its own body supplying it with an implement of such admirable consistency and adaptation as to enable it to excavate a habitation for itself, so accurately formed that to a casual observer it would appear a mystery how so perfect a circle could be produced. It is only on examination that the raised and hollow parts of the wood become visible, and explain, in some degree, the auger-shaped contrivance that has been used for the purpose of perforating.

It has already been stated, that the wood is perforated by a rotary motion of the foot, the adhering part of which acts as a fulcrum, carrying round the shells, and thus giving immense power to the animal in its operations.

It is said that when Brunei was considering how to construct the Thames Tunnel, he was one day “passing through the dockyard (at Chatham, where he was employed by Government), when his attention was attracted to an old piece of ship-timber which had been perforated by that well-known destroyer of timber—the Teredo navalis. He examined the perforations, and subsequently the animal. He found it armed with a pair of strong shelly valves, which enveloped its anterior integuments; and that, with its foot as a fulcrum, a rotatory motion was given by powerful muscles to the valves, which, acting on the wood like an auger, penetrated gradually but surely; and that, as the particles were removed, they were passed through a longitudinal fissure in the foot, which formed a canal to the mouth, and so were engorged. To imitate the action of this animal became Brunei’s study. ‘From these ideas,’ said he, ‘by slow and certain methods; which, when compared with the progress of works of art, will be found to be much more expeditious in the end.’”[18]

Professor Owen suggests that the power of the teredo to bore into wood depends on muscular friction, the muscular substance being perpetually renewed while the wood wastes away, of course, without renewal. Professor Forbes, Dr. Carpenter, and Dr. Lyon Playfair were appointed about twenty-five years ago by the British Association to examine into the natural history and habits of these boring animals, but they did not arrive at any definite conclusion as to whether the boring action of the teredo was mechanical or chemical. Dr. Deshayes, on his return from Algiers, after making accurate drawings and careful investigations, came to the conclusion that the borings were effected by an acid secretion. Mr. Thomson, of Belfast, examined the operations of the teredo on the pier at Port Patrick, and arrived at the same conclusion. The general opinion, however, is that the boring action is a mechanical one.

Although the teredo appears to penetrate all kinds of timber, that which it seems to destroy with the greatest ease is fir, in which it works much more speedily and successfully than in any other, and perhaps grows to the greatest size. In a fir pile, taken from the old pier-head at Southend, a worm was found 2 feet long and ¾ inch in diameter, and indeed they have been heard of 3 feet in length and 1 inch in diameter. The soft, porous nature of the wood is no doubt the cause of their rapid growth, for in oak timber they do not progress so fast, or grow to so great a length, though in Sir Hans Sloane’s ‘History of Jamaica’ (1725) there are accounts of these animals destroying keels of ships made of oak, and even of cedar, although the latter is renowned, by its smell and resin, for resisting all kinds of worms.

Shell left by the Teredo Navalis.

Cell formed by the Teredo Navalis showing method of boring.

There is another kind of worm which is very destructive to timber, which Smeaton observed in Bridlington piers. This is the Timber-boring Shrimp, or Gribble, the Limnoria terebrans (or Limnoria perforata, Leach), a mollusc of the family Asselotes, Leach. The Limnoria terebrans is very abundant around the British shores. Its ravages were first particularly observed in the year 1810, by the late Sir. Robert Stevenson, engineer of the Bell Rock Lighthouse. While engaged in the erection of that structure he found the timber of the temporary erections to be soon destroyed by the attacks of the limnoria. So little was known of the limnoria at the time that Dr. Leach, a well-known naturalist, who received some specimens from Mr. Stevenson, in 1811, declared it to be a new and highly interesting species. In 1834, the late Dr. John Coldstream wrote a very full and interesting description of the creature. The limnoria resembles a woodlouse, and is so small as hardly to be perceptible in the timber it attacks, being almost of the same colour. Small as is this crustacean, hardly larger indeed than a grain of rice, it is a sad pest wherever submarine timber is employed, for it works with great energy, and its vast numbers quite compensate for the small size of each individual; for as many as twenty thousand will appear on the surface of a piece of a pile only 12 inches square. It proceeds in a very methodical manner, and makes its way obliquely inward, unless it happens to meet a knot, when it passes round the obstacle and resumes its former direction. The surface of the timber being first attacked, it proceeds progressively into the wood to the depth of about 1½ inch: the tunnels being cylindrical, perfectly smooth winding holes, about ⅟16th inch in diameter: it is necessary that the holes should be filled with salt water. The outward crust formed by these attacks then becomes macerated and rotten, and is gradually washed away by the beating of the sea. The limnoria does not work by means of any tool or instrument like the teredo, but is supposed to possess some species of dissolvent liquor, furnished by the juices of the animal itself. Dr. Coldstream was of opinion that the animal effects its work by the use of its mandibles. From ligneous matter having been found in its viscera, some have concluded that it feeds on the wood, but since other molluscs of the same genus, Pholas, bore and destroy stonework, the perforation may serve only for the animal’s dwelling. The limnoria seems to prefer tender woods but the hardest do not escape: teak and greenheart are about the only woods it does not attack. The rate at which the limnoria bores into wood in pure salt water is said to be about one inch in a year; but instances have occurred in which the destruction has been much more rapid. At Lowestoft Harbour, square 14 inch piles were in three years eaten down to 4 inches square. At Greenock, a pile 12 inches square was eaten through in seven years. It is stated that a 3-inch oak plank, 12 feet long, would be entirely destroyed in about eight years. Joists of timber have been found at Southend Pier, 2 feet and 3 feet below high-water mark, where they had made rapid destruction. The limnoria almost always works just under neap tides; it cannot live in fresh water, and whilst it is destroying the surface of a pile, the teredo is attacking the interior: sometimes the former is found attacking the same timber as the Chelura. As with most of these creatures, the male limnoria is smaller than the female, being about one-third her size. The female may be distinguished by the pouch in which the eggs and afterwards the young are carried. About six or seven young are generally found in the pouch.

The Wood-boring Shrimp (Chelura terebrans) is a crustacean that nearly rivals the teredo itself in its destructive powers. It makes burrows into the wood, wherein it can conceal itself, and at the same time feast upon the fragments, as is proved by the presence of woody dust within its interior. Its tunnels are made in an oblique direction, not very deeply sunk below the surface, so that after a while the action of the waves washes away the thin shell, and leaves a number of grooves on the surface. Below these, again, the creature bores a fresh set of tunnels, which in their turn are washed away, so that the timber is soon destroyed in successive grooved flakes.

According to Mr. Allman, its habits can be very easily watched, as if it is merely placed in a tumbler of sea water, together with a piece of wood, it will forthwith proceed to work, and gnaw its way into the wood. The apparatus with which it works this destruction is a kind of file or rasp, which reduces the wood into minute fragments. In this creature the jaw feet are furnished with imperfect claws, and the tenth segment from the head is curiously prolonged into a large and long spine. The great flattened appendages near the tail seem to be merely used for the purpose of cleaning its burrow of wood dust which is not required for food. The creature always swims on its back, and when commencing its work of destruction, clings to the wood with the legs that proceed from the thorax. The wood-boring shrimp is one of the jumpers, and, like the sand hopper, can leap to a considerable height when placed on dry land. It has been detected in timber taken from the sea at Trieste. It was first observed as an inhabitant of the British seas several years ago, by Mr. Robert Ball, of Dublin, and in January, 1847, it was described by Mr. Mullins, C.E., in a paper read before the Institution of Civil Engineers of Ireland, as being very injurious to the timber piles in Kingstown Harbour, near Dublin, and far more destructive than the Limnoria terebrans.

LIMNORIA TEREBRANS. FEMALE. MALE.

A. B. C. HEAD OF THE TEREDO NAVALIS.

RASP OR FILE OF THE CHELURA. CHELURA TEREBRANS.

ELEVATION of PILES, SOUTHEND PIER, DESTROYED by the “TEREDO” and “LIMNORIA” ABOVE and BELOW the COPPER SHEATING.

We have already referred to the lesson the celebrated engineer, Brunel, received from observing the teredo; and we can state that architects have also received lessons from nature. Sir Christopher Wren constructed his spire of St. Bride’s Church, London, after observing the construction of the delicate shell, called Turretella, which has a central column, or newel, round which the spiral turns. Brunelleschi designed the dome of Sta. Maria, at Florence, after studying the bones of birds and the human form; and Michael Angelo followed Brunelleschi in constructing the dome of St. Peter’s, Rome.[19]

The Lepisma is also a destructive little animal, which begins to prey on wood in the East Indies, as soon as it is immersed in sea water. The unprotected bottom of a boat has been known to be eaten through by it in three or four weeks.

These worms, it must be remembered, do not live except where they have the action of the water almost every tide, nor do they live in the parts covered with sand. The wooden piles of embankments and sea locks suffer very much from their depredations, and in the sea dykes of Holland they cause very expensive annual repairs.

The Dutch used to coat their piles with a mixture of pitch and tar, and then strew small pieces of cockle and other shells, beaten almost to powder, and mixed with sea sand, which incrusted and armed the piles against the attacks of the teredo. We believe it was a frequent practice in London, about half a century ago, to place small shells in the wooden pugging between the floor joists to deaden sound.

Having described the chief peculiarities of these worms, shown their mode of working, and the extent to which their destructive powers may be carried, it will now be necessary to consider the various schemes which have been proposed and tried to prevent their desolating ravages. These may be divided into three classes, viz. the natural, chemical, and mechanical.

1st. By using woods which are able to resist the attacks of sea worms.

2nd. By subjecting piles to a chemical process.

3rd. By adopting a mechanical process.

First. We have not any English woods which resist their attacks. Elm (used for piles in England) or beech (used for piles, if entirely under water, in France) cannot withstand the teredo; while oak cannot battle successfully against wood-beetles in carvings. It is therefore necessary to inquire whether foreign woods are any better.[20] Unfortunately the great expense of importing them into England prevents their use for piles.

Nearly all our foreign woods used for engineering and building purposes come from the Baltic or Canada: they are fir and pine. Memel timber from the Baltic is comparatively useless unless thoroughly creosoted; and Canadian timber is not so good as the Baltic wood. At Liverpool and some of the western ports of England Canadian timber is preferred to Baltic, although we believe the reason to be that they cannot get the latter, except in small quantities at a time.

The following is a list of timber woods which, according to good authorities, resist for a long period of time the attacks of sea worms. It should be borne in mind, however, that the timber should be cut, during the proper season, from a large and full-grown tree; and, to prevent splitting, it should be kept from the direct action of the sun when first cut; it should have all the bark and sapwood removed, and allowed to dry a certain time before being used.