USES TO WHICH ASBESTOS IS APPLIED.
In regard to the many varied uses to which this mineral is now put, foremost must be placed the numerous valuable articles manufactured for engineering purposes.
Were I to attempt to enumerate the various kinds of packing, mostly in the shape of millboard, in use for all kinds of engines, for steam joints, cylinder and steam chest covers, pipe flanges, &c., this part of my little book would have the appearance of a manufacturer's catalogue.
The rapidly increasing favour with which high pressure steam is now regarded by engineers, recently necessitated the introduction of a packing capable of resisting the higher temperatures and pressures; as a consequence manufacturers of asbestos goods had to devise improved methods of manufacture in order to meet the new condition of things, and this they succeeded in doing in a way to give universal satisfaction.
For washers asbestos has many advantages over rubber; its weight is less, they can be frequently used, and half the thickness of rubber is mostly sufficient.
The fibre, Sir Frederick Abel says, is as effectual for closing the breeches of big guns so as to prevent the passage of gas, as for ensuring safety, in the same way, for miners' lamps. In these last, it had for a long time been found very difficult to get a good joint between the metallic and the glass parts of the safety lamp, and a great many different materials were tried for filling these joints in such a way that air should not be able to pass through. In many cases, the air was contaminated with a certain amount of gaseous material which would be likely to render the whole explosive, and if this got through the joint between the glass and the metal, there would be very serious risk of explosion. After a great number of substances had been tried and found unsatisfactory, some hundreds of experiments were made by Sir Frederick Abel and Sir Warington Smyth, with asbestos washers, which, in the end, were found to maintain their condition most admirably.
With regard to closing the breeches of big guns, we are informed also on the authority of Sir Frederick Abel, that the only contrivance which could be called an approach to a perfect arrangement, was one devised by a French artillery officer, M. Dubange, which consisted of a kind of pad of asbestos fibre attached to the breech-closing arrangement. This, from its mineral nature, was nearly indestructible, and, consequently, lasted without material deterioration for a great length of time, notwithstanding that it was subjected to the enormous pressures which are now developed in the bores of very heavy guns.
In connection with the Whitehead torpedoes, we learn from the same authority, that in these and other similar receptacles, within which charges of wet gun cotton are enclosed, the use of asbestos is now found to overcome a great difficulty. The vessels containing the damp cotton have to be soldered, in order to keep them perfectly air-tight, and thus prevent the water from escaping; and in order to do this, with anything approaching safety, the space between the gun cotton and the metal surfaces which have to be soldered, were formerly filled with damp felt wads or discs. This answered the purpose; but Sir Frederick Abel states that it was found after they had been stored for some time, that the effect of the moisture on the felt was to cause it to undergo a kind of decay or fermentation, resulting in the formation of gas to such an extent that the vessels were distended, and threatened to burst, and sometimes actually did burst with considerable violence. Asbestos millboard was then substituted for the felt, and the difficulty and danger were then removed; gas was no longer evolved, whilst the operation of soldering could be performed with safety, the material remaining perfectly unaltered.
In the manufacture of time-fuzes again, asbestos washers are found most valuable. Washers of india-rubber and wash-leather were formerly used, but these in time became hard, and acted on the metal surfaces with which they came in contact in such a manner as to cement them together, instead of keeping them mobile, and it was not until the introduction of asbestos washers that difficulties in connection with the proper action of these ingenious contrivances for the explosion of shells in a given time after their discharge, were removed.
One of the latest uses to which asbestos has been proposed to be applied in connection with warfare is as a coating for ironclads. It is alleged by the inventor of the process that if asbestos be packed between the armour-plates it will arrest, or certainly minimise, the inflow of water after the penetration of a ship's side below the water-line. This has already been tried by the Admiralty, and an interesting account of the trial may be found in the Army and Navy Gazette Supplement, for August 28, of last year, and in the Globe of the previous evening. Should the results of further trials corroborate the success of the first, it is manifest that a great impetus will be given to the asbestos trade, whilst it will, at the same time, raise confidence in our fighting ships, by practically preventing them from becoming waterlogged in action.
An eminent firm of manufacturers in New York have recently supplied, under contract with the United States Government, a quilting for boiler covers for their model warships, the Dolphin, Chicago, Atlantic, and Boston. These quiltings weigh about two pounds to the square foot, and are at all times removable. The same firm make removable pipe coverings a speciality.
Certainly some of the uses to which this mineral is now being put are sufficiently astonishing. Who, for instance, could have imagined that a substance of such comparative specific gravity as crude asbestos could have been manufactured into a cloth available for aeronautical purposes in which absence of weight is of such primary importance? Yet here it appears to be the one thing wanting to give success to that despair of aeronauts, military ballooning. Many years have now passed away since scientific military men first turned their attention to this subject; and it is now long since the War Department of the Government first authorized experiments to be made with the view of utilising balloons in warfare, and notwithstanding all the time and money which has been expended, until now the result in the way of practical success has been nil. No use of balloons was made even in the late Egyptian campaign, which shows that up to that date English military men had no great faith in their usefulness or availability.
The difficulties to be encountered are doubtless sufficiently formidable. Gas, it is clear, could not be carried into a hostile country or into remote and nearly inaccessible districts. Even if procurable at all near the battle-field it could only be obtained by a long and difficult process of generation at the very time when speed and simplicity would be the main factors of success. Gas, therefore, being practically out of the question, it seems to have occurred to Mr. Spencer, the well-known balloon manufacturer, that it would be better after all to revert to the original conception of Montgolfier. The old-fashioned fire-ball, which acquired its power of ascension from rarefied air produced by burning straw or something similar, was, of course, of far too dangerous a character, and had been productive of far too many fatal accidents. It remained, therefore, to construct a balloon of some uninflammable material, in order to obviate this difficulty; and with the assistance of his friend, Mr. Fisher, the Secretary of the United Asbestos Company of London, he ultimately succeeded in so doing. A balloon was accordingly constructed, the whole of the lower part of which was formed of fine asbestos cloth, and the remainder of canvas, covered with a fireproof solution. The first trial took place in the grounds of the Welsh Harp, at Hendon, and this has since been repeated at Chatham, under the inspection of the Royal Engineers' Committee, and on both occasions, I am informed, with success. The balloon, which was a model only, stood about 30 feet high, and was suspended between two uprights, between which it hung down like a limp rag. It was of a cylindrical shape, having a deep zone at the equator, and a containing capacity of about 300 feet. Attached to the neck was a copper spirit-lamp. As soon as a light was put to the spirit the inflation commenced, and the balloon was fully distended in a space of about five minutes.
The immense advantage gained by this method over the tedious and difficult process of inflation by gas, even under the most favourable circumstances, is sufficiently obvious, whilst it is at the same time apparent that the quantity of spirit requisite for an endless number of ascents could be carried about with the greatest facility. Another advantage remains to be considered, in that whilst the large volume of gas required for an ordinary balloon is in itself deleterious, the rarefied air in the new fireproof balloon is perfectly innocuous, and it can be raised or lowered at will simply by turning the neck of the lamp a little up or down. It is perhaps somewhat superfluous to say that the Russian Government at once adopted these balloons for war purposes.
In further continuance of this part of the subject, that is the application of asbestos to matters connected with warfare, the particulars of a very interesting experiment, which may have an important bearing on the carriage of explosive material in time of war, was given by Mr. Boyd, the manager of the United Asbestos Company's works at Harefield, of whom I have already spoken, and to whom I have been considerably indebted for much practical information, in a paper read by him before the Society of Arts, on an occasion when, through his kindness, I had an opportunity of being present. He was referring to the value of asbestos millboard as a lining for fireproof cases and deed boxes. The matter, he said, was put to a practical test thus: two iron rails were supported on brickwork at a height of about eighteen inches from the ground, and underneath them a strong fire of wood shavings and chips was made, and when this had well burnt up, a deed box filled with papers was pushed along the rails to the centre of the fire, where it was completely enveloped in the flames, and there it remained for a space of twenty minutes. On the box being withdrawn it unlocked easily, and the papers were found in perfect preservation, being neither charred nor discoloured.
On seeing this result, one of the gentlemen present asked if the boxes could not be used for transporting gunpowder or other explosive substances. A quarter of a pound of powder was then put in a small bag, and placed inside a fresh box, which was pushed along the rails into the centre of the fire, to which fresh fuel had been added. Those present withdrew to a respectful distance, evidently, said Mr. Boyd, not yet having absolute faith in the heat-resisting properties of asbestos; and after the box had been exposed to the fire for twenty minutes the question naturally arose how it was to be got off again. The manager himself performed that operation by means of a long iron rod and hook, after which the box was again opened and the powder found intact. The question was then asked by some one present who was not yet satisfied, "Why have the powder in a bag? Let it be laid on the bottom of the box loose." This was done, and the fire ordeal repeated, again with the same result. Nothing could well be more interesting or more suggestive to every one connected with the asbestos industry than the foregoing.
As a final instance of its applicability for purposes connected with warfare, it may be interesting to mention that I have lately seen it stated that the fibre would be of great value for use as lint in hospitals and on the battle-field. Of this I am unable to speak, but if it be a fact that it can be so used in favourable comparison with the best lint, as stated, it is certain that its imperishable quality would be of great advantage, seeing that it could be used over and over again, only needing to be purified by passing it through fire after each time of using.
In regard to the use of asbestos in connection with building operations, much attention is now being given to this in a variety of ways, in America especially. The building laws of Boston, New York, and Philadelphia pay special attention to this, and many material alterations have been required to be made in consequence in the fittings of several important public buildings, whilst the use of the mineral is, I believe, rendered compulsory on those wishing to procure licences for the erection of new theatres, libraries, concert halls, &c. At the American Academy of Music, in Philadelphia, the underwriters went so far as to offer a reduction of one per cent. per annum provided an asbestos curtain was placed in the house. The Fire Apparatus Committee then, it is reported, succeeded in perfecting "the only barrier of complete protection to an audience against fire in the world." This curtain, made of asbestos cloth (97 per cent. pure asbestos and 3 per cent. cotton) is 54 feet wide and 53 feet high. It is hung on wire lines, three-eighths of an inch thick, connecting with a drum located in the apex of the roof, and can be raised with ease by two men and lowered by one.
Again, after the disaster at the Ring Strasse Theatre, at Vienna, when attention was drawn to the great danger arising from the want of some certain and rapidly applicable means of separating the stage from the body of the theatre, the Roman Minister of Public Security issued an order that every theatre should be fitted with a fireproof curtain capable of entirely isolating the stage from the theatre, and he indicated an asbestos cloth curtain as one that would meet the case. All the principal Roman theatres are now supplied with these curtains, the material having been furnished by the United Asbestos Company of London. The same company has also recently fitted a similar curtain for use at the Theatre Royal in Manchester. This is formed of an iron frame holding the asbestos curtain.
Asbestos fireproof curtains are also in use at the New National Theatre, Washington; the Criterion, Brooklyn; and in the theatre at Cleveland, Ohio. They have also lately been supplied to several English theatres, as well as that at Manchester just mentioned.
The terrible calamity at the Opéra Comique in Paris, coupled with that which so recently occurred at the burning of the theatre at Exeter, again set men's minds running in the direction of greater security from fire in theatres. As a consequence several varieties of curtains, all involving the use of asbestos, have been contrived. For instance, at the building of that pretty little theatre (Terry's) in the Strand it was resolved to replace the usual heavy, cumbrous, slow-lifting iron shield by a single light-grey asbestos curtain, which moves up and down as easily as an ordinary window-blind. And the authorities agree that this is as valuable a protection to the audience as the former ponderous iron portcullis which, winding slowly up and down, was calculated to depress the nerves of the audience in the same way that passers-by in the street are affected by the harsh grating of the iron shop shutters when being wound down for the night.
Again, in the proposals for a new "Safety Theatre," brought to the notice of the public by Mr. Henry Irving, stress is naturally laid on the necessity of sealing the stage, or shutting it off from the auditorium, so that in the event of fire its perils might be confined to itself, and to providing an outlet for the smoke, which is often more disastrous in its effects even than the flames. This he proposed to accomplish by means of an asbestos curtain which, on being dropped, would at once become rigid with the wall on either side. This curtain was proposed to be worked in iron grooves going straight up to the gridiron floor; and the suggestion was made that this should be used as constantly as the ordinary act-drop, there being at the same time nothing to prevent its being made as ornamental as the usual curtain. It could also be worked as easily, and be just as easily lifted for a recall. The audience, it was said, would thus have the satisfaction of knowing that every time the curtain was dropped they were effectually protected by a fireproof screen, which could be lowered with the same rapidity as the present curtain.
In continuation of this subject it may be worth mentioning, as showing the amount of attention which is now being directed to this important matter, that an experiment was recently made in the neighbourhood of Oxford Street to test the fire-resisting qualities of another new curtain for the stage, said to have been invented by Captain Heath. This experiment took place within a specially built hoarding, within which there was erected a large model of the Drury Lane stage proscenium. Captain Heath explained to the company, invited to witness the experiment, that the curtain was made of asbestos and canvas, and was rolled on a block of wood placed underneath the front part of the stage, where it occupied an otherwise useless space, and in no way interfered with the business of the theatre. The sides of the model were made of iron plates, and the front entirely of wood. When certain catches were released counterbalancing weights came into action, and the curtain was run rapidly up from below. On reaching the top, it pressed tightly and automatically against the back of the proscenium, turning on at the same time a supply of water from a perforated pipe which ran along the whole length of the top of the curtain so as to keep it constantly wet. The arrangement of the switch used for communicating action to the curtain was such as to turn on the water and close the curtain against the sides at will. He also stated that communication with the lever of the switch could be fitted to any part of the theatre. A very severe fire test was employed. The model was first filled with inflammable materials such as shavings and large blocks of wood, over which petroleum was poured. At a given signal the curtain was raised and the fire lighted. The flames at once rose, accompanied with volumes of smoke, none of which, however, found their way to the front of the proscenium. The interior looked like a furnace. But so effectually were the flames shut off that it was possible to sit on the fore part of the stage without feeling the heat, the only thing noticeable being the steam arising from the wet canvas. This, Captain Heath explained, might be obviated by painting the canvas in oils. The fire burned fiercely for half an hour, and the universal opinion of those present was that the curtain was perfectly fireproof, and that its construction was as simple as it was useful for the purpose intended.
Whilst these sheets are still in the press, yet another theatre dies the apparently natural death of all such structures, that is, by fire. Portugal is this time the scene of the disaster, the sufferer being the Baquet Theatre in Oporto. The calamity was caused by the wings catching fire from a gas-jet, whereby the whole of the stage scenery was almost, immediately afterwards enveloped in flames, the furious progress of which it was found impossible to arrest. Here, then, was a striking instance of a holocaust being caused by the want of such a curtain as has been described; for, had such a thing been available, the stage would have been at once shut off from the auditorium, and even if it had not been found possible to save the structure, the fire, at any rate, would have been localised for a sufficient length of time, to have enabled the authorities to clear the building, and so have prevented the panic and horror which ensued, and the fearful sacrifice of life which humanity now deplores.
It is worth while perhaps recording the foregoing, because there can be very little doubt that something of this kind will presently be made compulsory even in England for use in theatres and music halls generally. And it is believed, from the course matters are now taking in the United States, that the use of asbestos in some form or other will be made compulsory there for the shelvings and doors of public libraries and places for the custody of records, for sheathings between wooden floorings and below carpets, for hearthstones, for the linings and doors of elevators or lifts, and for the better preservation of Pullman cars from fire.
The premises of the American Watch Case Company, of Toronto, have their floorings protected by an asbestos covering, and I saw an announcement recently in the Sherbrooke Gazette that this covering had saved their premises from destruction by a fire which had occurred there. In connection with this part of the subject it may be added that various attempts have been made for the introduction of asbestos into the manufacture of lace curtains, dresses, &c., but I believe that the principal obstacle in the way of success in this line lies in the fact that in its present state, in the shape of curtains, for instance, it is found to be an obstinate holder of dust. This objection will, no doubt, be presently got rid of; and soon we may hope to have heard the last of those fearful scenes which have at times occurred from the firing of ladies' dresses at the footlights in theatres.
The Chevalier Aldini's idea, previously mentioned, has been recently revived in Paris, the firemen there having been furnished with asbestos clothes. Immediately after this was done it was reported in the papers that on a conflagration occurring in the basement of a building there, the firemen arrived, clad in their asbestos suits, and were thereby enabled to descend at once into the basement, where they extinguished the fire in a very short time, and so prevented what might have been a great calamity. And according to the papers it appears that the same course is now about to be taken in England, and the London firemen at any rate protected in a similar manner; and there can be little doubt that this course will presently be universally adopted for the protection of the men engaged in saving life and property from destruction by fire. Nothing has yet been discovered that will equal asbestos for this purpose. It will neither burn nor smoulder, and is as impervious to fire as well made mackintosh is to water.
Manufactured into cloth and paper, it is in use in sugar refineries, chemical laboratories, &c., for straining and other purposes, especially for filtering acids and similar fluids. A coarser kind of cloth is used for stokers and furnacemen's aprons, for salvage blankets, and gloves. A special quality of glove made of asbestos cloth, lined with rubber, is supplied for electric light work.
A further development of the industry is indicated by the announcement that a New York manufacturing firm has recently taken over a large contract for the manufacture of mail bags out of asbestos cloth.
It is also proposed to be used as an inner sole or lining for boots and shoes with the object of keeping the feet warm in winter and cool in summer, the material possessing the double advantage of being at once a preserver of heat and a protector from cold.
For cold storage buildings it will doubtless be found invaluable. There are buildings in New York, principally for fish preservation, which are built with double walls surrounding the cold chambers, having some kind of non-conducting material between the walls by way of lining. For this purpose asbestos would be unsurpassed, and the cheap No. 3 quality would answer perfectly well.
Mr. Boyd, in the lecture before referred to, says that some years ago, when resident at Genoa, he was one of the members of a committee for procuring a new floating chapel for the use of seamen. The old chapel was built on the deck of a hulk, but the extremely high summer temperature caused the repairs to be both frequent and costly. The committee therefore wanted the new chapel to be built of iron, but were deterred by the fear that its roof and sides, exposed to the sun, would get so hot as to render the interior unbearable. He therefore proposed to fill up the space between the outer skin and the inner boarding with asbestos ground to a rough powder; and this suggestion was adopted, the powder being tightly rammed in by the carpenters. The result, he informs us, was so successful that whilst the outside temperature stood at 100°, the temperature inside, when doors and windows were kept shut, did not exceed 70°. And he therefore suggests that asbestos powder might be used in a similar way for rendering the deck cabins of steamers navigating the Red Sea and Suez Canal more comfortable for the passengers.
For wall and ornamental papers it is being largely used, and a superior quality of asbestos writing paper is now being made in Paris. One can easily imagine a great future in this line for asbestos paper written or printed on with asbestos ink for all kinds of registers and permanent records, bankers' and merchants' books, and the like. One of the leading manufacturers in New York already prints his price lists on asbestos paper. And another has on show fine papers as susceptible of receiving good impressions from type as any in use in modern books. Coloured wall papers also are manufactured in great variety, which are not merely incombustible, but practically indestructible by fire; and which retain, even after severe heat tests, their colourings, markings and letterings as clearly impressed and as vividly visible as before. Boards also are made of asbestos, varying from the thinnest and lightest card to heavy shelving, fit either for partitions in safes or for use in large libraries.
In a recent number of "L'Industrie Moderne" I found an account of a new process invented by a Mr. Ladewig for manufacturing pulp and paper from asbestos fibre, which he asserts will not only resist the action of both fire and water, but will absorb no moisture; this pulp, he says, may be used as a stuffing and for the joints of engines. He further proposes to use it in the form of a solid cardboard as a roofing material for light structures.
The process of manufacture consists in mixing about 25 per cent. of asbestos fibre with about 25 or 35 per cent. of powdered sulphate of alumina. This mixture is moistened with an aqueous solution of chloride of zinc. The mixture is washed with water and then treated with an aqueous solution of ammoniacal gas. The mixture is again washed and then treated with a solution composed of one part of resin soap and eight or ten parts of water mixed with an equal bulk of sulphate of alumina, which should be us pure as possible. The mixture thus obtained should have a slightly pulpy consistency. Finally, there is added to it 35 per cent. of powdered asbestos and 5 to 8 per cent. of white barytes. This pulp is treated with water in an ordinary paper machine, and worked just like paper pulp.
In order to manufacture a solid cardboard from asbestos which shall be proof against fire and water and capable of serving as a roofing material, sheets of common cardboard, tarred or otherwise prepared, are covered with the pulp. The application is made in a paper machine, the pulp being allowed to flow over the cardboard. Among other uses, the asbestos paper has been recommended for the manufacture of cigarettes, though its applicability for this purpose is not so readily seen.
Manufactured into paint, the demand for it is continually increasing. It is used in the Houses of Parliament, as it was in very large quantities at the several recent exhibitions at South Kensington.
In the form of cement there is nothing equal to it as an efficient covering for boilers, steam pipes, hotblast furnaces, stills, &c. For this purpose it is made of about the consistency of mortar and spread on with a trowel in the ordinary way. Certain chemical ingredients have to be added, which, while not injurious to the metal, cause the asbestos to adhere firmly to the plates, so that when dry it becomes quite hard and can be walked over without being injured. With a boiler carrying say 80 lbs. steam pressure, the application of from 1½ to 2 inches of this composition so well retains the heat in the boiler, that a thermometer with the bulb held close to the outer surface of the covering will not indicate more than 80° to 85° Fahrenheit. Boilers, steam pipes, &c., covered in with this composition will, it is asserted by the manufacturers, effect a saving of as much as 33 per cent. in fuel.[10]
This cement, which is made from a very cheap quality of asbestos, is now in common use in Canada and the States, where, as already shown, it is found to operate with a twofold effect, viz. by lowering the temperature of the boilerhouse, to the great comfort of the engineers and firemen, and also, in a very marked degree, economising the expenditure for fuel. It seems, therefore, strange that its use in this country has as yet made so little headway. In one of the large palatial buildings recently erected in London, where engines are required to be in constant work for pumping water for working the lifts and for general purposes, as well as for the dynamos, the heat from the boilers forms so great a nuisance, and occasions so much loss in other ways, that very considerable expense is about to be incurred, with a view to lowering the temperature. When conversing recently with an expert on this subject I asked whether the use of asbestos would not effect the desired object. Yes, he answered, it would, but it is too expensive. This certainly seems very strange, as I know that the cement composition referred to is made of the very commonest quality of asbestos, of the refuse, in point of fact, which could probably be used for no other purpose. The expense, therefore, cannot be great, and as to its mode of use, it is simply laid on with a trowel, like mortar or any similar composition, and when once done is singularly effective. I have stood in an engine-house where the boilers were covered with about two inches in thickness of this cement, which then showed a hard, dry, firm surface; and, when the engines were in full work, on placing one's hand on the covering there was little more than a gentle warmth perceptible on the outside surface of the composition, whilst the surrounding atmosphere was scarcely, if at all, affected by the heat from the boilers. The boiler quiltings referred to on a previous page as being manufactured by a New York firm under contract with the United States Government, for use in some of their model war ships, would no doubt be as effectual for the purpose, but naturally they would be more costly, being an altogether different contrivance, and made so as to be easily removable when required, which, of course, is not the case with the so-called cement. There is little doubt, however, that, although the use of asbestos in this form does not seem to find much favour here, its use for the purpose of coating boilers and steam-pipes will presently become as general in England as it already is on the other side, where its valuable qualities seem to be so much better known and appreciated.
Improved stove pipings are now being manufactured in the States which in appearance exactly resemble cast-iron. These have the additional valuable properties of extreme lightness, combined with great strength and a capability of ornamentation unobtainable with the usual cast-iron pipes mostly in use; paint in the case of the asbestos pipes not scaling off under heat as it will do in the case of ordinary iron pipes. The manufacturers of these pipes claim for them that they combine the strength of steel with the lightness of paper. Tubes also are made for electrical engineers which provide them with a non-conducting covering for their wires both fire and waterproof, so as to preserve the perfect insulation of the wire.
Asbestos rope is used for fire escapes and similar purposes, as well as for the transmission of power over places exposed to heat. In dyeing and printing cloth it is frequently necessary to hang the fabric in loops from parallel rods for exposure to steam, air or ammonia. In order that it should hold upon the rods, without straining or slipping, rope or strips of cloth are usually wound around the poles, but this does not remove, although it mitigates, the difficulty, because the heat and corrosive action of the vapours will rot any covering; the first notice of the deterioration being generally the appearance of small pieces of rod covering among the cloth which is in process of finishing. Asbestos rope and cloth are now largely manufactured and used for this purpose in the United States with very beneficial results.
In commenting on the recent loss of life occasioned by the panic at the fire at the Exeter Theatre, a well-known journal, speaking of the various modes of providing for escape, mentions the case of a man of fashion, a millionaire, who died not long ago, and says that he would never go to bed in a strange house without having an apparatus of knotted rope affixed to a ring in the wall, by which he might lower himself to the ground on an emergency. But, asks the journalist, what if the rope itself took fire? The answer naturally is, let it be an asbestos rope, then it will neither burn nor rot.
The use of the fibre in the manufacture of gas stoves is too well known to need any remark.
As a lubricant it is unrivalled.
Another very important use to which it is now being applied is in the manufacture of filters. These are specially useful where the liquid to be filtered is of a caustic or strongly acid nature, or where the filter with residue is to be ignited without consuming the filter, or where the residue is to be subsequently dissolved off the filter by acids or other solvents. In many cases a very finely divided asbestos is desirable. This is accomplished by a process recently patented in Germany by Fr. Breyer, of Vienna. The asbestos is first coarsely ground, and then mixed with some granular crystalline carbonate, which must be soluble in acids. The carbonate should possess a hardness between 3 and 4, 5, according to the mineralogical scale. The mixture is ultimately ground together in a mill. Afterwards the mass is treated with an acid until the carbonate has been dissolved out. The escaping carbonic gas causes the asbestos fibres to be loosened and disintegrated from each other so as to render the mass porous. Of course it must be thoroughly washed with water before being used.
Again, in the purification of foul gas, as well as for ventilating and deodorizing man-holes for cesspools, sewers, &c., its use is found to be unsurpassed by any other known material.
Mr. Boyd, in the paper so often referred to, says in regard to this, that he was some time previously asked to supply asbestos yarn spun in such a way as to have good capillary action, and, on making inquiry, found it was to be used for the above purpose. In describing the mode of using it, he says that there is placed over the opening rising from the sewer a hood of galvanized wire, interlaced with this asbestos yarn, the ends of the yarn dipping into a receptacle filled with liquid disinfectant, which, as they become saturated, form a disinfecting screen, through the meshes of which the gases rise, and in their passage through are purified and rendered innocuous. The system hitherto previously adopted for deodorizing sewer gas has been to cause it to rise through charcoal, but it is found that the impurities soon clog this up, and simply prevent the passage of the gas, whereas in the arrangement just mentioned (which is that of Messrs. Adams & Co., of York), the gas rises freely, and is perfectly deodorized.
There are, of course, very numerous other applications of the material which might be referred to or described, but probably those already mentioned are the most important and the most interesting; and these, it is hoped, are at any rate sufficient to indicate the great value of this singular mineral product, as well as to confirm the statement with which I started, that this is indeed one of Nature's most marvellous productions.