they chiefly contained generalizations of phenomena. 89. Mr. De Luc's Letters to Prof. Blumenbach, contain the exposition of the whole of his system. 90. Acquiescence of Messrs. de Dolomieu and de Saussure in his opinions respecting the small an- › tiquity of our continents. 91, 92. Little attention paid to his writings by Dr. Hutton and Mr. Playfair. 93. The above question must ultimately be decided by facts. 94. Mr. Playfair's opinion that the present line of our coasts, with their gulphs and promontories, has been formed by the action of the sea. 95. The tendency of that action is, on the contrary, to fill up gulphs, and to destroy promontories, originally existing around our continents. 96. The fragments of rock which fall from the cliffs, being impelled against them by the waves, form in time an elevated beach at their foot: the action of the sea, therefore, could not have originally produced those cliffs, which, by this process, it tends to place beyond the reach of its waves. 97. Mr. Playfair's own description of the phenomena of low coasts proves that no action of the sea could have produced cliffs. The gain of the land on the coasts is not wholly at the expense of the higher grounds, but results, in a great measure, from the sand of the sea itself. 97. a. The cascades falling down into the princi pal valley, and the semi-cones of rubbish formed under them against its sides, disprove Mr. Playfair's assertion that none of the lateral vallies join it at either too high or too low a level. 98, 99. Mr. Playfair infers the remote antiquity of our continents from successive platforms of alluvial land on the sides of vallies in which rivers flow. 100. Such platforms do not consist of alluvial land. 101. Alluvial land is disposed in horizontal strata, of which the lowest always contain the largest materials; but in these platforms, the strata are often inclined, and the gravel is most commonly above the sand. 102. Operations of rivers in loose soils. 103. Rivers, which traverse their own alluvial land, run, in dry seasons, on a level lower than that of the adjacent grounds. 104. Those which run always lower, either on both sides, or on one only, have cut their channels in original sails; hence result three distinct cases: 1st, Where their action has gradually cut through an eminence composed of loose materials, round which they have not been able to wind. 105. 2dly, Where they have attacked and cut off a promontory in their way, forming it into an abrupt cliff, while they have

left

stream.

left a peculiar kind of alluvial land on the opposite side of their 106. 3dly, Where their course has chanced to lie at the foot of an original cliff of loose materials; in which case there is no alluvial land on the opposite side. 106. a. In all these cases, the sections of the strata are shown on the banks, and may easily be distinguished from those of alluvial land. 107. The dissimilarity of the strata on the opposite sides of rivers maintained in opposition to Mr. Playfair's assertion of their identity. 108. In what manner a lapidary would naturally reason, if informed of Mr. Playfair's comparison between the way in which a river had cut its course through a rock, and that in which he divides a block of marble with his saw. 109 110. What conclusions a lapidary, thus led to meditate, would probably draw respecting the disorder prevalent in the strata. 111, 112. Inconsistency of ascribing the formation of loose strata to the rivers, and yet supposing those rivers to have sunk their beds in loose strata, when they first began to flow, 113, 114. Huttonian opinions relative to the migration of stones. 115. Lakes oppose a strong check to the system of the waste produced by running waters. 116-120. Mr. Playfair's account of the process by which lakes have been filled up, and cataracts effaced. 121. He speaks of the lake of Geneva as forming an exception to other lakes. 122, 123. The law of changes applied in the Huttonian theory to an alternation of continents on this globe. 124. Mr. Playfair's first attempt to account for the lake of Geneva, by supposing an uncertainty with regard to its original dimensions. 125. Those dimensions ascertained by a circumstance mentioned by himself. 126, 127. The furrows on the side of Mont Salève, supposed by M. de Saussure to be traces of a current, are really effects of the partial subsidences of separated masses of the strata. 128. Had the level of the lake ever stood as high as Mr. Playfair supposes, its dimensions would still have been too small to contain the sediments of the Rhone and its tributary streams, if the vallies in which they flow had really been excavated by them. 129. The other phenomena of the tract of ground, which would then have formed its basin, disagree with Mr. Playfair's own account of alluvial land. 130. Mr. Playfair's second hypothesis of the production of this Jake by the dissolution of a saline stratum. 131-134. How far

Mr. Playfair adheres to the rules of philosophical investigation, which he particularly claims in this inquiry. 135-137. No accurate judgment can be formed of the circumstances respecting the lake of Geneva, without a full consideration of that whole space, surrounded by mountains, of which it occupies only a part. Description, from M. de Saussure, of the defile of L'Ecluse. 138. Of Mont Salève. 139. Remarks on it, 140. Of Les Voirons. 141. Remarks on the difference between that mountain and Salève. 142. The original horizontality of strata proved by the phenomenon of the breccias. 143–145. Of the Rocks of Meillerie, and the coast of the lake from Tour ronde to St. Gingough. 146. Of the rocks of St. Tryphon and Champigny, the mountains on the left bank of the Rhone and the lake, and the Val de Lie. 145. a. These descriptions clearly point out the true cause of the production of vallies and of the cavities of lakes, since they show the parts where fractures took place in the strata, and the different degrees of depression suffered by the separated masses. 146. a. The attention of geological observers ought to be particularly directed to these effects. 147. Of the lakes of Jura. 148. Of the Dent de Vaulion. 149. Of the manner in which the above lakes are drained. 150. Of Val-orbe. 151-157. Remarks and inferences. 158. Use of details concerning phenomena. M. de Saussure's description of the lakes of Neuchatel, Bienne, and Morat. 159. These three lakes were formerly united. 160 Evident marks of depression in those spots. 161. Remarkable situation of a considerable mass of marle. 162. The dipping of the strata under the waters of the lakes points out where the masses sunk, by the depression of which those cavities were formed. 163. Of the lake of Annecy. 164. Additional details respecting the mountains which surround it. 165. Les Bornes. 166. Valley between that mountain and Salève. M. de Saussure's description of the Brezon. 167. Of the valley of Faucigny. 168. A correspondence between salient and retreating angles is frequent in narrow callies, which are commonly the effect of a single fracture; but not in large vallies, which are produced by two fractures, with a depression of the intermediate part. M. de Saussure's description of the Monts Vergi. 168. a. Of the Mole, and of the mountains which follow it. 169. Of the

Vallée

Vallée du Reposoir. 170. Of the lake of Bourguet. 171. Deductions from the foregoing descriptions, that the lake of Geneva forms no exception to other lakes; that its cavity does not owe its production to any local cause, but to the same which produced all the basins of other lakes, and all vallies; and that the effects of that cause are plainly visible in the surrounding scenery. 172. That cause acknowledged by Mr. Playfair, unconnected as it is with his other hypotheses: his opinions respecting partial elevations and depressions. 173. Concerning the phenomena of shifts in mines. 174, Concerning the angular motion of the strata, and the supposed existence of an expanding power, directed from the centre toward the circumference. 174. a. The angular movements of the strata will afford a fair criterion of the two opposite theories of subsidence and elevation. 175. The masses, which form our mountains, could not have undergone those motions, unless, by the subsidence of other masses, and the consequent production of vullies, spaces had been afforded them in which they could freely turn. 176. Mr. Playfair's statement of the Huttonian theory with respect to the expanding power of heat. 177, 178. He considers as separately demonstrated the two propositions on which it rests; viz. the elevation of our continents from the bottom of the sea, and the consolidation, by heat, of the mineral strata. 179. Examination of the probability of the existence of such a power, and of the mode of its action. 180. Mr. Playfair deduces its existence from the impossibility that any other power but that of fusion could have consolidated the materials of destroyed continents at the bottom of the sea. 181. The power of fusion is not, however, a power of elevation; the intermediate idea of expansion is wanting. Not heat itself, but only an expansible fluid produced by heat, could have power, by its density, to clevate the mass of our continents; and no sooner should that mass be fractured, than the fluid would escape through the openings, and the mass would sink down again in ruins. 182. Mr. Playfair provides against this objection, by supposing the breaches and separations in the strata to be completely filled up by unstratified minerals. 183. Necessity of therefore examining whether these breaches are actually filled up.' 184-186. Metallic veins considered with this view their contents shown to be stratified. 187. Little import

ance of closing these passages, since the subsequent formation of caverns must have supplied so many others for the escape of the expansible fluid. 188. Basaltes and whinstone, having undergone the same catastrophes as the other strata, cannot be considered as instruments in those very catastrophes. 189, 190. The supposition that the materials for one set of continents are supplied by the waste of another, and carried down by running waters to the sea, is refuted by the impossibility that such substances, necessarily intermingled confusedly with eachother, should in the sea, be separated according to their respective genera and species, and laid over its bed in distinct strata. 191. Proofs of the non-existence of a great internal heat of the globe, from the remains of marine animals found in our continents, and from the intermixture of loose with stony strata. 193. System of chemical precipitations. 194. Since our mineral strata were certainly formed at the bottom of the ancient sea, their máterials must either have proceeded from the lands which surrounded it, or have been separated from the liquid which composed it. Peremptory exclusion of the first of these propositions. 195. Establishment of the second. 196. The elementary ingredients of the primordial liquid being now dispersed in combinations which are but imperfectly known to us, we cannot ascend to the primordial operations by specific affinities. 197. Impossibility of recomposing mineral substances with the coercible ingredients furnished by our analyses. 198. The greatest part of the ingredients, now composing the known substances of our globe, were contained in the primordial liquid, and separated from it by successive precipitations, produced by the ascent of new ingredients, and the escape of those expansible fluids by which our atmosphere was formed. 199. Dr. Hutton's exposition of his hypothesis respecting the expansive power of heat. 200. He considers this power as exercised by an expansible fluid, which he calls fiery vapour. 201. He deduces the first proof of his theory from the. situation of volcanoes on the highest mountains. 202. The second, from lavas found among the strata of the earth. 203. Account of the elevation of the new island, near Santorini. 204, 205. Want of analogy between this volcanic operation, and the supposed elevation of our mineral strata. 206-208. The sinking down of volcanic cones is an exemplification of the manner in