THE HABITS OF FISHES.
The following notes as to the habits of fish may prove of interest to the naturalist:—
“It has often been observed in the course of the Bell Rock operations, that during the cold weather of spring and autumn, and even at all seasons, in stormy weather, when the sea is much agitated by wind, the fishes disappear entirely from the vicinity of the rock, probably retreating into much deeper water, from which they do not seem to return until a change of weather has taken place; so much was this attended to by the seamen employed on this service, that they frequently prognosticated and judged of the weather from this habit of the fishes as well as from the appearance of the sky.”
“It was a general remark at the Bell Rock that fish were never plenty in its neighbourhood, excepting in good weather. Indeed, the seamen used to speculate about the state of the weather from their success in fishing. When the fish disappeared at the rock, it was considered a sure indication that a gale was not far off, as the fish seemed to seek shelter in deeper water, from the roughness of the sea, during these changes of the weather. This evening, the landing master’s crew brought to the rock a quantity of newly caught cod fish, measuring from fifteen to twenty-four inches in length. The membrane called the sound, which is attached to the backbone of fishes, being understood to contain, at different times, greater portions of azote and of oxygen than common air, the present favourable opportunity was embraced for collecting a quantity of this gas in a drinking glass inverted into a pail of salt water. The fish being held under this glass as a receiver, their bladders were punctured, and a considerable quantity of gas was thus collected. A lighted match was afterwards carefully introduced into the glass, when the gas exhibited in a considerable degree the bright and luminous flame which an excess of oxygen is known to produce.”
On showing this extract to my friend Dr. P. D. Handyside, who has contributed some interesting papers to the Royal Society of Edinburgh on the Polyodon gladius, he writes:—“Biot and De La Roche found that the proportion of oxygen in the air bladder increases with the depth of the water in which the fish usually lives, from a small quantity up to 87 per cent. Biot found in the deep Mediterranean fishes 87 parts of oxygen, nitrogen, and carbonic acid. Humboldt found in the electrical eel 96 parts of nitrogen and 4 only of oxygen. No hydrogen has ever been detected in this organ. In the air bladder of marine fishes oxygen predominates, and in that of fresh-water fishes nitrogen. No air sacs exist in rays, flounders, sole, turbot, and others which lie at the bottom.”
Dr. Handyside adds: “The extract shows with what a practical and accurate mind your father was endowed, and I think, in justice to him, you should give his observations.”
I also communicated Mr. Stevenson’s papers on fishings to the Honble. B. F. Primrose, C.B. (Secretary to the Fishery Board: Scotland), who has kindly sent me a letter explaining why the progress of the fishings in the Shetland Islands is slow, from which I give a few extracts:—
“I have read with great interest your father’s notes upon the fisheries of Scotland. They bear distinctly the impress of that practical and accurate mind with which he is described as having been endowed. It is also pleasant to see that his mind went a great deal further, and grasped the application of science to solve the mystery of fishings.
“He seems to have overlooked, as was universal in his day, that the secret of fisheries is not the presence of fish but the certainty of markets. Samuel Laing of Orkney, to whom he refers, was, I think, the first that struck this key note of truth. The Dutch came here and fished for herrings because they could not fill their vessels fast enough for the markets behind them in Holland. The Shetlanders did not fish for herrings because they had no remunerative market for them, but they fished, and fished boldly, where they had one, viz., for the whales of the Arctic Regions. They might have brought the herring home from off their own coasts and got nothing for them, but they could not bring the whale oil home without a secured profit.
“The same thing obtains still. Shetland, from its position, cannot compete with the mainland of Scotland either in the home market or in the great continental markets for herrings; but it yields large supplies of cod, ling, and tusk, for which it pushes distant adventures to Iceland and the Faroe Isles.”
CHAPTER XV.
MARINE SURVEYING.
Modern engineers who have practised only under the benign reign of Ordnance Surveys and Admiralty Charts, can have no idea of the toil their predecessors underwent in procuring data for their designs and reports; and I am safe in saying that Mr. Stevenson was of all others the engineer to whom in his sea coast practice, such useful aids would have been of the very highest value.
For example, before he could tell, with the exactness he desired, the distance between the Bell Rock Lighthouse and the shore, he had, in absence of any reliable information, to undertake a pretty extensive trigonometrical survey of the coast, involving the measurement of a base line upwards of two miles in length—a most “laborious operation,” he observes, in which his assistants were aided by six sailors from the lighthouse tender.
Again, to show the difficulty in determining the best site for a lighthouse in those early days, before an accurate Government survey of the coast line had been made, I give from Mr. Stevenson’s Journal the following notes of his observations to determine the best site for a lighthouse at Kinnairdhead in Aberdeenshire. I give them at length, as jotted down at the time, for they may perhaps lead young engineers of the present day to be thankful that, in most cases at least, they are not, from want of accurate coast surveys and soundings, left to resort altogether to their own resources in getting the information they require. But I think they are specially worthy of record as showing the extreme care bestowed by Mr. Stevenson in getting the data to enable him to determine the exact positions of the several lighthouses he designed. His Journal says:—
“First.—I caused a mast to be erected upon the top of Kinnairdhead Castle or Lighthouse, making its extreme height from the ground 100 feet.
“Got the yacht under weigh, and having a careful pilot on board, I sailed for Rattray Head, and there observed the mast over the land of Cairnbulg, it being then high water, or twenty minutes past 7 P.M. With the parapet of the lighthouse in view, have eight fathoms water off the head, which bore W.N.W. Run in upon the head with flag upon the mast seen over the land till seven fathoms water, when the flag disappeared. Then leave the vessel and sound from the boat, and have 6 fathoms, 5, 5, 4¼, 3, 2, 1 fathom, and lastly 3½ feet. Return to the ship in a more southerly direction, and have 3 feet, 1 fathom, 2, 2¼, 2¾, 3½, 4, 4¾, 5, 5½, 6½, and 7 fathoms. All these soundings rocky bottom.
“With the Windmill near Peterhead on with Stirling hill, and Monument hill on with the rounded Sandy Down of Rattray, and the parapet of Kinnairdhead Lighthouse seen over Cairnbulg land, you are in 8 fathoms water off Rattray Briggs, which lie about ¼ of a mile to the southward of the Sandy Down.
“Wait off the Briggs till the light was seen, then stood in upon the Briggs till the light was shut in by the land of Cairnbulg, and at that moment had 8 fathoms water, so that at present the light forms an excellent direction for Rattray Briggs.
“Find that the lightroom is seen fully from the yacht’s deck in 8 fathoms water off Rattray Briggs, that the flag upon the masthead is seen in 6 fathoms water—high water spring tides. Ship then bearing from the head E.S.E. and W.N.W., distant about one mile from the shore, where a man is distinctly observed at a boat in the twilight.
“Secondly.—Remove the mast from the castle or lighthouse on the morning of the 15th to Cairnbulg, and elevate a flag to the height of 86 feet from the ground, or 97 feet from high water mark, at the distance of about 100 yards from the high water mark at the point connected with Cairnbulg Briggs.
“The yacht lying off or to the westward of the Briggs, was got under weigh at 2 A.M. of the 16th, and beat up the north shore as far as Rosehearty, and there observed the flag over the land. Found off Rosehearty that the flag was just hid by the highest inequalities of the land to the southward of the Castle, and that it appeared at the lower or flat places sometimes in sight 20 feet above the land, and at other places intercepted by the land and houses of the town, amongst which it often appeared and disappeared. The range of the flag along the land was as far as Mr. Dalrymple’s house when it was time to put about, having there three fathoms at nearly low water.
“After completing the observations in this direction, sailed along the shore southwards to Rattray Briggs. Find that Inverallochy head, south-eastward of the town of Cairnbulg, is the eastmost point on this coast, but, being at a distance from the foul ground of Cairnbulg, would make a less desirable point than Cairnbulg.
“Off Rattray, in eight fathoms water, begin to lose sight of the lantern on Kinnairdhead Castle as before. See the mast and flag at Cairnbulg a considerable way up the country over the lands of Inverallochy. See the flag, standing in upon Rattray to five fathoms water at half tide, lose it, and then stand for Fraserburgh.
“As the result of these trials, find that Inverallochy head or point is the most eastern or projecting point of land upon that coast, that Cairnbulg is the next projecting point. The former lies between the points of danger, viz., Rattray and Cairnbulg.
“Find that if the light were to be moved to a more southern situation, it would be better on either of the above places than Rattray Head, which would entirely remove its usefulness from the Moray Firth.
“Find that in the event of two lights for this coast, the one ought to be at Kinnairdhead, and the other upon the Cock Inch at Peterhead.
“Under all the circumstances of the case, find that it would be most advisable to erect a new lighthouse at Kinnairdhead, about 100 yards more to the eastward than the Castle stands, and erect it about twenty or thirty feet higher than the Castle. This, with a better light, would perhaps answer the general purposes of the coast better than a single light placed on any of the other stations along this coast.”
After perusing this extract, the reader, I think, will not be surprised to find Mr. Stevenson making an urgent appeal on behalf of all interested—Seamen—Fishermen, and Engineers, for a Government Survey and “Sailing Directions” of the intricate navigation of the shores of Scotland, which he did in the following terms:—
“The attention which Government has long paid to the improvement of the Highlands and Islands of Scotland, in connection with the British Fisheries, has been attended with the best effects in the country at large. It is much to be wished that these shores were rendered more accessible to the mariner.
“The marine survey of the Highlands by Murdoch Mackenzie, undertaken by order of the Lords of the Admiralty, may be considered as the first grand step towards the improvement of the Highlands, and next to that the later institution of the Northern Lighthouses. By means of these the fisher may find his way from loch to loch, and the mariner bound over seas, instead as formerly of holding a course without the Lewis Islands, can now find his way through the Sounds, and in adverse winds take shelter in safe harbours, instead of being exposed to the boisterous seas of the Atlantic Ocean; these charts and lighthouses have in many points of view contributed to the improvement of the Highlands, and to the present flourishing trade carried on through these Sounds from Liverpool, etc., to the northern continent of Europe. However, from the extensive range of coast which these charts include, together with the prodigious number of extensive lochs and small islands, it was impossible that any first survey could be made so accurate as to supply the place of pilots, where there are neither landmarks to characterise the coast, nor beacons or buoys to point out the situation of sunk rocks; and although these charts have certainly contributed much to the facility and security of the navigation of the Highlands, yet no one will say that they are free from imperfections, and their incommodious size and high price are insurmountable bars to their general utility, thereby rendering them impracticable for the use of small vessels, so that they are only to be found in the cabins of large vessels, where large accommodation affords room to unfold them, but even here also the price forms an objection, as the charts are always found by the shipmaster.
“Nothing therefore can be more necessary or essential to the improvement of the Highlands and Islands of Scotland, than an accurate survey of the fishing grounds, lochs, and harbours, upon a scale considerably larger than Mackenzie’s charts, given in the form of a book of the size of a large quarto, containing only the lochs, etc., interleaved with printed directions and descriptions of each chart or harbour, which book of charts, accompanied with a general chart would sufficiently guide the mariner and fisher in their several pursuits.
“With regard to an accurate survey of the lochs and harbours in the Highlands published in the most commodious form for the use of small vessels, such an undertaking would require to be sanctioned in a manner similar to the survey undertaken by Murdoch Mackenzie, and though in process of time the sale of these charts might produce a considerable return to those concerned with it, yet the time and attention which such (with a laborious number of soundings) must occupy would certainly require that those concerned in the undertaking should be put in possession of certain sums of money to enable them to go on with that deliberation which is essential to accuracy, and this encouragement should be the more considerable that the charts might be procured to the public at a moderate price.”
This Memorial, written in 1803, was intended for and in some shape communicated to the Admiralty, and was followed by good results.
In “A Memoir of the Hydrographical Department of the Admiralty,” published in 1868,[13] are the following remarks:—“It was about this time,” 1810, “that the Admiralty first conferred on the Hydrographer the privilege of selecting a surveyor for the home coasts. Singular as it may appear, the Hydrographer had at this time great difficulty in finding a naval officer competent to fill the position, or who was acquainted with anything beyond surveying by common compass. At length, however, about 1811, Mr. George Thomas, a master, was selected” for home service. The Memoir also states that at the same time the Hydrographer appointed to foreign service Mr. Beaufort, afterwards Sir Francis Beaufort, the eminent Hydrographer to the Admiralty, who was, all his life, Mr. Stevenson’s intimate friend and constant correspondent.
There is therefore, I believe, no reason to doubt that Mr. Stevenson’s original appeal and subsequent personal friendly and free intercourse with the officials of the Admiralty led to the establishment, on a systematic footing, of our Government “Admiralty Survey,” which, as all engineers know, indicates with marvellous accuracy and detail every shoal, sunken rock, and sounding on the coasts of Great Britain and Ireland; and from which the “Admiralty Sailing Directions” have been prepared with such discernment and care that the whole system of our coast survey may now be said to have attained perfection.
With Colonel Colby, also, of the Royal Engineers, who was Director of the Ordnance Survey, Mr. Stevenson regularly corresponded, being no less interested in the progress of the great national work so successfully carried on under his charge.
CHAPTER XVI.
CONTRIBUTIONS ON ENGINEERING AND SCIENTIFIC SUBJECTS.
Contributions to Encyclopædia Britannica and Edinburgh Encyclopædia—The alveus or bed of the German Ocean—Sectio planography—Wasting effects of the sea at the Mersey and Dee—Density of fresh and salt water—The Hydrophore.
We have seen that Mr. Stevenson’s college education was mainly, if not altogether, due to his own thirst for knowledge, and his education being voluntarily undertaken, could hardly fail to issue in good results. That his early studies were of incalculable value to him no one can doubt; and his own conviction of this may explain the solicitude with which, in after life, he impressed on his sons the extreme importance of being properly grounded in every branch of study, scientific and practical, which a well trained engineer has to call to his aid in the practice of his profession.
Fortified by this valuable training, Mr. Stevenson had also that unselfish love of his profession which alone can move a man to give the results of his experience freely to others, and this he did to the Edinburgh Encyclopædia and the Encyclopædia Britannica, in articles on “Roads,” “Lighthouses,” “Railways,” “Dredging,” “Blasting,” and other engineering subjects.
But he did not confine his literary labours to matters purely professional. His love for nature in all its aspects led him also to make communications to the Scientific Journals of the day on subjects of more general interest. Of these his papers “On the Alveus or Bed of the German Ocean,” in which by an investigation of many evidences he is led to the conclusion that the sea is gradually encroaching on the land, may be quoted as an example.
Mr. Stevenson’s first communication on this subject was published in 1816, in vol. ii. of the Wernerian Transactions, in which he gives examples, from actual observation, of the wasting effects of the sea on various parts of the coasts of the British Isles. His second communication was made to the Wernerian Society in March 1820, and published in the Edinburgh Philosophical Journal of that year.
In the fifth edition of Baron Cuvier’s “Essay on the Theory of the Earth,” reference is made to Mr. Stevenson’s theory. His papers are several times quoted in Lyell’s Principles of Geology, and the General Committee of the British Association at York in 1834 passed a resolution, “that Mr. Stevenson be requested to report to the next meeting upon the waste and extension of the land on the east coast of Britain, and upon the general question of the permanence of the level of the sea and land, and that individuals who may be able to supply information upon the subject be requested to correspond with him.”
Without discussing in how far Mr. Stevenson’s theory may be sound (for on such questions it is notorious that the views of geologists do not always coincide), it cannot be denied that his mode of dealing with the subject is original and interesting, and as the papers are not now accessible to the general reader, it may be excusable to give one of them in extenso. I also notice another feature which gives interest to the subject. In his illustrations he adopted a mode of representation which was peculiarly suitable for the object in view. It will be seen from [Plate XII.] that the sections are laid down on what is now known by engineers as sectio planography, which it is believed was used for the first time in illustrating this paper.