which our continents would have sunk, if their elevation had been produced by expansible fluids, which must have escaped through, fissures in their vault. 209, 210. Evident stability of the state in which depressed masses rest on the bottom of pre-existing caverns into which they had sunk, and impossibility of the suspension of fractured continents over caverns formed by the very act of their elevation. 211, 212, Indignation of Mr. Playfair against M. De Luc's theory, and explanation of the mistake by which it has been excited. 213. The Huttonian theory assumes the fusion of granite, in order that the consequent raising of this substance may appear to have filled up the interstices of the broken strata, and cemented the whole of the vault. 214, 215. Process of volcanic eruptions, and impossibility of applying that process to melted granite. 216. Great importance of the question, whether granite is a product of fusion, or a result of chemical precipitations. 217. Mr. Playfair's singular inference from the crystals of granite, and misrepresentation of M. de Saussure's opinion respecting that substance. 218. M. de Saussure's real opinion shown from his works. 219. His description of the Aiguille du Midi. 220. His acknowledgment of an error in his first account of it. 221. His demonstration of the stratification of granite. 222. Mr. De Luc's opinion on the subject decided by that demonstration. 223. Mr. Playfair supposes the extravasation of granite to have been prevented by the schistus, which formed an exterior crust. 224. Granite, while in a state of fusion, could not have obstructed the escape of the expansible fluids. 225. Phenomenon of the blocks of granite, and other stones, scattered over the surface in various parts of our continents. 226-229. The possibility of their stransportation by running waters, from mountains, whence they had been originally detached, opposed by Mr. De Luc, on account of the interposition of mountainous ridges, over which they could not have been conveyed; but maintained by Mr. Playfair, on the hypothesis that their migration had taken place, before vallies had been excavated, or mountains cut into their present form. 230. The operations supposed in this hypothesis could not have been executed in any time, however prolonged, unless means of action should also have been supplied. 231. No blocks of granite could have been detached from the supposed

convex mass of solid strata, at the summit only of which the granite had originally appeared. 232. Could blocks have been produced on such summits, no torrents could have been formed there to put them in motion. 233. The glaciers supposed by Mr. Playfair to have been powerful engines for the transportation of blocks. 234. The only fragments accumulated on glaciers are those detached from the steep sides of superincumbent rocks. 235. Mr. Playfair supposes that the waste of the soil under the blocks may have been one cause of their migration. 236-238. Phenomenon of rocking stones; whence he considers an unequal decomposition of the surface of blocks as another probable cause of their migration. 239. M. de Saussure's description of the valley of Urseren. 240. Of the valley and lake of Oberalp. 241. Remarks on these descriptions. 242. They are opposed to the consequence deduced by Mr. Playfair from M. de Saussure's account of a mass of lapis ollaris in the valley of Urseren. 243. Mr. Playfair's objection to the introduction of extraordinary causes in geological disquisitions. 244. He considers as such the débacle of M. de Saussure, but avoids mentioning the deluge, as illustrated by Mr. De Luc. 245. No theory contains more extraordinary causes than Dr. Hutton's. 246. M. de Saussure, by his débacle, intended only the retreat of the sea from the new continents, which is a fact. 247. He ascribed, however, too much power to that retreat, and to early torrents. 248, 249. The principle that the force of running waters is the smallest at the most elevated point, which Mr. Playfair adduces in proof that they have excavated the vallies, proves the contrary in the very valley which he takes as an example. 250, 251. M. de Saussure's description of this valley, lying between the Col de Ferret and the Col de Seigne. 252. Of the lake.

254. The small

of Combal. 253. Of the Glacier de Miage. quantity of the stones deposited at the extremity of the glaciers is a proof that the accumulation cannot have been the work of many ages. 255. In deducing the origin of the blocks of granite from granitic mountains, their genus only has been considered; whereas their species ought also to be examined. 256. The granite of the blocks is frequently very dissimilar from that of the nearest granitic mountains. 257. The same circumstance attends blocks of various other genera. Mr. Playfair's suppo

9

sition that the flints on the Blackdown hills are the remains of decomposed limestone strata. 258, 259. Gravel of granulated quartz in sandstone near Birmingham, supposed by him to have been produced upon the continents since their birth. 260, 261. The detailed examination of these hypotheses referred to Mr. De Luc's Travels. 262. Quantities of large blocks of granulated quartz in some counties of England. 263. Mr. Playfair's persuasion of the proportion which prevails between the size of stones, and the vicinity of the mountains whence he supposes them to have proceeded. 264. Such a proportion would exist, were stones really derived from mountains; but with respect to the scattered blocks and gravel, the fact is directly contrary. 265. M. de Saussure's description of the plain of Lombardy. 266. Impossibility of supposing an uniform declivity from the central point of the Alps to that plain ever to have existed. 267. No vestiges are to be found of any track which could have been pursued by the blocks now scattered in various parts of Germany. 268. Blocks of granite found at the bottom of a bed of fossile peat, under stony strata, in Mount Mesner. 269, 270. Large masses of calcareous stone, in a valley in Hildesheim, of a nature different from that of all the neighbouring calcareous mountains. 271. Phenomena of a similar kind in Ireland. 272. Repetitions of catastrophes were continued in the parts which now constitute plains, much longer than in mountainous tracts.-Sandhills in the lower parts of Piedmont and Lombardy contain marine shells and leaves of trees, which appear as if nearly recent. 273, 274. Mr. Playfair's opinion on the hill of Supergue near Turin refuted from the situation of the strata which compose that hill. 275, 276. The freshness of the marine shells found in that and the neighbouring hills affords a sufficient proof that many ages cannot have elapsed since those countries were abandoned by the sea. 277. Distinction between the terreau, or cultivated part of the loose soil, and the vege table mould produced by the decomposition of vegetables: the accumulation of the latter on original soils forming a true chronometer. 278. The supposed migration of stones fully refuted by the facts which have been stated. 279. No theory entitled to confidence, which does not afford an explanation of the phenomenon of the scattered blocks. 279, a.-281. The two

rival

rival theories of elevation and of subsidence considered with a view to that phenomenon. 282, 283. Necessity, in the former, of supposing the blocks to have travelled in some manner upon the surface; since their ejection from within by the expansible fluids, liberated in that very act, must have been immediately followed by the sinking of the raised continents: 284. In the theory of subsidence, the expansible fluids contained in the caverns must have increased so much in density from the enormous pressure exercised on them by the subsiding masses, as to have rushed out through the intervals of those masses with an irresistible impetuosity, throwing up to the surface whatever fragments they encountered in their way. 285. The lowest strata of the masses having suffered the greatest collision, their fragments are found on the surface in the greatest abundance; those fragments varying in species, in a manner correspondent with what is known of the strata themselves., 286. Importance of local lithologies, for the purpose of improving our acquaintance with the internal parts of our continents: 287. The conflict produced between the water making way into the caverns during the descent of the great masses, and the expansible fluids then rushing out, was a cause of the trituration and dispersion of the fragments on the bottom of the sea, far more powerful than any action of water upon the continents. 288. Necessity of atten tively considering the subject in every part. 289. Mr. Playfair invited to farther discussion. 290. REVIEW OF THE POINTS ESTABLISHED BY THE PRECEDING INVESTIGATIONS. 291. Of the data respecting events previous to the birth of our continents, contained in the foregoing conclusions. 292. The proofs of these propositions too much diversified to be detailed in this work. 293. They depend in part on experimental philosophy and chemistry: 294. And in part on the monuments remaining of the action of past causes, which monuments cannot be distinguished, without determining the state of our continents at their birth. 295. The great geological questions connected with the latter objects are brought forward generally in this work; and their particular proofs will be given in Mr. De Luc's Travels. 296. Common successions of strata in the Alps. 297. Their order different in different countries. 298. This subject requires to be farther illustrated by future observations.

299. All

299. All our knowledge of the mineral strata is derived from their catastrophes, by which masses of the inferior strata have been raised up, and thus brought to sight. 300, General im portance of the subject. 301. Introduction to an appendix, containing remarks on some of Sir James Hall's experiments, and Mr. Kirwan's Geological Essays.

REMARKS ON SOME EXPERIMENTS OF SIR JAMES HALL.

§ 302. These experiments have been considered as a confirmation of Dr. Hutton's hypothesis respecting the fixed air in the calcareous strata, which he supposed to have been prevented by the pressure of the ocean from escaping, when subjected to a consolidating heat. 303-306. Short account of those experiments. 307, 308. Analogy between them, and some which have been made on aqueous vapour, in supposed opposition to Mr. De Luc's theory of evaporation, 309, 310. Mr. De Luc's reply to the latter. 311. Application of that reply to Sir J. Hall's experiments; showing the difference between the resistance of a solid, which in them was opposed to the production of the fixed air, and the pressure of the ocean, which that fluid would be able to pervade with the same facility, with which aqueous zapour pervades the atmosphere. 312. Could the inference drawn from these experiments be maintained, it would really be fatal to Dr. Hutton's theory; since it would prove that the expansible' fluid, supposed, in that theory, to have elevated the whole mass of strata, could never have been formed under the pressure of that mass, in addition to that of the occan.

§313. Mr. Kirwan's object, as well as Mr. De Luc's, is to support the authority of Genesis, by confuting the systems in opposition to it. 314. Mr. Kirwan, though eminent in chemistry and mineralogy, has himself but little examined the various

phenomena