^{page 143 note *} Illustrations, art. 345, page 385.

^{page 144 note *} Let AD be Jura, and BC Mont-Blanc. Let D be the place on Jura where the blocks lie; the line DC will be the outline of the supposed surface. Let AB be drawn horizontally at the level of the surface of the lake, and DE at a level 2000 feet higher, meeting BC in E. We have then AB=DE=54 miles=285120 feet; and CE=CB—EB=14432–2000=12432 feet. The measure of this declivity along CD may therefore be easily obtained. Thus, CE: ED:: 12432 feet: 285120:: 1: 22.9, nearly one in twenty-three. Mr Playfair states it at one in thirty; but he has reckoned to the summit of Jura; whereas the blocks under consideration lie at some distance below that summit.

Let CF be equal to 7500 feet, and let FG be drawn horizontally; then G will be the lowest point of perpetual snow upon the supposed surface. The horizontal distance of G from the centre will thus be obtained, CE: CF:: ED: FG, or 12432: 7500:: 54 miles: 32½ miles. Let H be the extreme point of the granitic mass at the Buet, and let HK be drawn vertically; the point K will denote the limit of the granite upon the supposed surface.

^{page 145 note *} He supposes, that below the firm crust of the earth, then lying horizontally at the bottom of the sea, a set of caverns once existed, filled with peculiar elastic fluids. That at a certain period, this crust breaking to pieces, fell with great violence into these caverns, and drove out the elastic fluids contained in them with such impetuosity, that the blocks of granite under consideration, which then constituted portions of the lower part of the crust, were forced upwards into the air, and fell back into their present position.

^{page 148 note *} I need scarcely say, that by the term Plutonic, I mean to characterize that geological system in which the principal agent is heat acting under Compression.

^{page 149 note *} This observation meets an objection urged against Dr Hutton by M. de Breislac, a gentleman to whom I feel indebted for the handsome manner in which he has mentioned the result of my experiments, and who, on most occasions, has treated our views with peculiar fairness, but who seems in this important article to have altogether misapprehended the system proposed. In his late work, (Introduction à la Geologie, tr. Fr. p. 115.) he urges as subversive of Dr Hutton's views, some thermometrical observations in which the bottom of the sea was found to be as cold as its surface. To urge this as an objection, implies that the heat employed in this system is supposed to be for ever, and everywhere, acting upon the sand of the sea; whereas it is well known that Dr Hutton conceived that the subterranean heat, as well as that of the volcanoes, was subject to short fits of activity, with ages of intermission.

^{page 151 note *} He says, “the inhabitants had scarcely begun to recover from their first terror, when they saw themselves plunged into new alarms; at ten minutes past eleven, they saw, rolling towards the city, a tide of the sea, which passed over the parapet of sixty feet, above the ordinary level of the water; at thirty minutes past eleven came a second tide, and these two were followed by four others of the same kind, at fifty minutes past eleven; at twelve o'clock, thirty minutes; one o'clock, ten minutes; one o'clock, fifty minutes. The tides continued, with some intervals, till the evening, but lessening. They have ruined one hundred toiees of the rampart, part of which, of three toises length, and of their whole thickness, were carried by the torrent fifty paces.” It is remarkable, that in these six waves, the two first intervals of time are exactly of twenty minutes each, and the three others of forty. It is probable, that they have all resulted from one great impulse.

^{page 152 note *} Philosophical Transactions, vol. XLIX. p. 433. The retreat is here said to have begun an hour and a half after the shock.

^{page 160 note *} This aid, by which our diluvian wave is so much assisted, can be of no such service to M. de Saussure's hypothesis, as he has originally framed it. He conceives (art. 210, p. 141. vol. i.) that, at a period when the mountains were covered with water, the crust was broken which defended certain caverns then void, and the waters rushing into them with violence, left the mountains in their present state, and, by their retreat, produced the diluvian torrent. It is plain that such a torrent could derive no assistance from the blocks of ice. For when this water, in its previously stagnated state, touched the solid earth, if any blocks of ice were there, they would adhere to that solid mass, and would not be carried off by the retiring waters; and where this water lay deep upon the solid mass, its ice, if it had any, must have been floating at the surface, and could not be attached to blocks of stone, lying of course at the bottom.

It is obvious, from the mode in which this topic is introduced by M. de Saussure, (which he does, as he expressly says, to meet the impatience of his reader,) that he is not satisfied with it himself, nor can it bear the slightest examination.

^{page 161 note *} This elevation may be illustrated, by the familiar example of what happens in the act of digging a piece of firm soil. The gardener first thrusts his spade into the unbroken ground, then leaning on the handle, gradually forces the flat iron upwards; by this means, a heave of the soil takes place; the middle part being raised, while the sides remain more or less attached to the firm soil. A separation between the two is the consequence; and a formation of rents open upwards, which gradually become wider and wider as the spade rises.