Page:Blackwood's Magazine volume 002.djvu/28

EXTRACT OF A LETTER FROM MR SCORESBY, JUN. M.W.S. &c. TO PROFESSOR JAMESON.

Whitby, 27th Aug. 1817.

MY DEAR SIR,

That man is born to disappointment, and that where he indulges the highest expectations he is frequently deceived, are truths which I doubt not but you, my dear sir, may be disposed to admit. At least I assure myself, you will feel a sympathy in the disappointment I now allude to, the particulars of which I am about to communicate.

Last year, you will recollect, I made an experiment on the impregnation of wood with sea-water, when submitted to vast pressure, by being immersed some thousands of feet deep in the sea, the result of which was interesting. From this experiment, and two others subsequently made, I perceived, that small blocks of wood, sent down to the depth of 720 feet, became a little impregnated with water, but were still buoyant in this fluid; that similar masses of oak, fir, beech, &c. after being sunk to the depth of 4000 feet, became heavier than sea-water, but that the fir speedily regained some of its buoyancy, so that it floated in fresh water; that at the depth of 4566 feet, lignum vitæ, hickery, elm, beech, mahogany, and fir wood, as well as bone, each became more or less impregnated with water, so that they all sunk in salt water, and having been kept constantly immersed, yet remain of greater specific gravity than the water of the sea. From the observable ratio of increase of specific gravity, obtained by wood subjected to an increase of pressure, I imagined that a still higher pressure would produce a still greater effect, and that the proportion of weight, gained by certain descriptions of wood sent down by a line, might be made use of to ascertain the depth. To prove this point, I wished to try the effect of pressure at the depth of a mile or a mile and a half. I therefore prepared for the experiment by providing blocks of wood of different shapes, dimensions, and qualities, and other substances, to the amount of twenty articles. In this assortment I had blocks of fir, oak, and hickery, in cubes, parallelipoids, and wedges of different weights. The wedges and parallelipoids, each, contained two cubic inches, and the cubes eight; from which I expected to find whether the shape or dimension of the wood had any effect in encouraging or hindering the entrance of the sea-water. A counterpart of each substance, corresponding in size, shape, and weight, were in readiness to be immersed in a tub of water during the time the principal pieces were under water, that the clear effect of the impregnation might be ascertained. Besides the above interesting object, I had in view other matters also—the temperature of the sea at a depth scarcely before sounded was to be ascertained—the water of the greatest depth to which the apparatus was sent, to be brought up, and its specific gravity and constituents examined—two tin vessels (sent by Mr Adie), intended for trying the depth and mean specific gravity of the water passed through in the descent, to be proved—the nature of the current to be examined—and by means of a frame of wire-gauze stretched across the upper valve of the marine diver, it was converted into a trap for insects and small fishes; and whatever animals might enter by the lower valve in its descent, were expected to be brought up by it.

With these various objects in view, I procured all the lead lines I could meet with, and having a favourable opportunity on the 28th of June, I moved the ship to a field of ice, fixed the whole apparatus, consisting of the marine diver, a Six’s thermometer, Mr Adie’s tin vessels, the specimens of wood, bones, jet metals, &c. and allowed them to sink to the perpendicular depth of 720 feet without meeting with the bottom. The end of the line resting in a boat, was, after an interval of two hours, taken on board the ship, and by a slow and steady motion, we proceeded to draw it in. We had taken about 300 yards on board, when, to my excessive mortification, the line gave way, slipped through the grasp of a man who held it at the time, and disappeared in a moment! Thus an experiment in which I placed such sanguine expectations, was blasted—an experiment which I intended as a finishing one, proved so indeed by another and reverse process. The apparatus I set a high value upon, being the only one of the kind in existence. The original was presented me by Sir Joseph Banks, and contrived at his re-