The Project Gutenberg eBook of Principles of Geology by Sir Charles Lyell.

138 The speculations which follow, on the ancient physical geography of Siberia, and its former fitness as a residence for the mammoth, were first given in their present form in my 4th edition, June, 1835. Recently Sir R. Murchison and his companions in their great work on the Geology of Russia, 1845 (vol. i. p. 497), have, in citing this chapter, declared that their investigations have led them to similar conclusions. Professor Owen, in his excellent History of British Fossil Mammalia, 1844, p. 261, et seq., observes that the teeth of the mammoth differ from those of the living Asiatic or African elephant in having a larger proportion of dense enamel, which may have enabled it to subsist on the coarser ligneous tissues of trees and shrubs. In short, he is of opinion, that the structure of its teeth, as well as the nature of its epidermis and coverings, may have made it "a meet companion for the reindeer."

139 Pallas, Reise in Russ. Reiche, pp. 409, 410.

140 Nov. Com. Petrop. vol. xvii. p. 584.

141 Nov. Com. Petrop. vol. xvii. p. 591.

142 Quart. Journ. Geol. Soc. Lond. vol. iv. p. 10, Memoirs.

143 Journal du Nord, St. Petersburg, 1807.

144 Fleming, Ed. New Phil. Journ., No. xii. p. 285.

Bishop Heber informs us (Narr. of a Journey through the Upper Provinces of India, vol. ii. p. 166-219), that in the lower range of the Himalaya mountains, in the northeastern borders of the Delhi territory, between lat. 29° and 30°, he saw an Indian elephant of a small size, covered with shaggy hair. But this variety must be exceedingly rare; for Mr. Royle (late superintendent of the East India Company's Botanic Garden at Saharunpore) has assured me, that being in India when Heber's Journal appeared, and having never seen or heard of such elephants, he made the strictest inquiries respecting the fact, and was never able to obtain any evidence in corroboration. Mr. Royle resided at Saharunpore, lat. 30° N., upon the extreme northern limits of the range of the elephant. Mr. Everest also declares that he has been equally unsuccessful in finding any one aware of the existence of such a variety or breed of the animal, though one solitary individual was mentioned to him as having been seen at Delhi, with a good deal of long hair upon it. The greatest elevation, says Mr. E., at which the wild elephant is found in the mountains to the north of Bengal, is at a place called Nahun, about 4000 feet above the level of the sea, and in the 31st degree of N. lat., where the mean yearly temperature may be about 64° Fahrenheit, and the difference between winter and summer very great, equal to about 36° F., the month of January averaging 45°, and June, the hottest month, 81° F. (Everest on climate of Foss. Eleph., Journ. of Asiat. Soc., No. 25, p. 21.)

145 See Dr. Buckland's description of these bones, Appen. to Beechy's Voy.

146 Darwin, Journal of Travels in S. America, &c., 1832-36, in voyage of H. M. S. Beagle, p. 98. 2d Ed. London, 1845, p. 86.

147 Darwin, Journal of Travels in S. America, &c., p. 99, 2d Ed. p. 85.

148 Burchell, cited by Darwin, ibid. p. 101. 2d Ed. p. 87.

149 Since the above passage was first printed in a former edition, June, 1835, it has been shown by the observations of Sir R. Murchison, M. de Verneuil, and Count Keyserling, and more recently by M. Middendorf (see above, p. 81), that the Lowland of Siberia has actually been extended, since the existing species of shells inhabited the northern seas.

150 Humboldt, Fragmens Asiatiques, tom. ii. p. 393.

151 Reboul. Geol. de la Période Quaternaire, who cites Observ. sur la Sibérie, Bibl. Univ., Juillet, 1832.

152 Conjectured to be the wild stock of Bos grunniens.

153 Recollections of a Journey through Tartary, Thibet, and China (ch. xv. p. 234), by M. Huc. Longman, 1852.

154 For an account of the more modern changes of the tertiary fauna and flora of the British Isles and adjoining countries, and particularly those facts which relate to the "glacial epoch," see an admirable essay by Prof. E. Forbes. Memoirs of Geol. Survey of Great Brit. vol. i. p. 336. London, 1846. To this important memoir I shall have frequent occasion to refer in the sequel.

155 See a paper by Charles J. F. Bunbury, Esq., Journ. of Geol. Soc., London, No. 6, p. 88. 1846.

156 The Calamites were formerly regarded by Adolphe Brongniart as belonging to the tribe of Equisetaceæ; but he is now inclined to refer them to the class of gymnogens, or gymnospermous exogens, which includes the Coniferæ and Cycadeæ. Lepidodendron appears to have been either a gigantic form of the lycopodium tribe, or, as Dr. Lindley thinks, intermediate between the lycopodia and the fir tribe. The Sigillariæ were formerly supposed by Ad. Brongniart, to be arborescent ferns; but the discovery of their internal structure, and of their leaves, has since proved that they have no real affinity to ferns. According to the view now taken of their structure, their nearest allies in the recent world are the genera Cycas and Zamia; while Corda, on the other hand, maintains that they were closely related to the succulent euphorbias. Stigmaria is now generally admitted to have been merely the root of sigillaria. The scalariform vessels of these two genera are not conclusive in proving them to have a real affinity with ferns, as Mr. Brown has discovered the same structure of vessels in Myzodendron, a genus allied to the mistletoe; and Corda has lately shown that in two species of Stigmaria, hardly distinguishable by external characters, the vessels of the one are scalariform, and of the other dotted.

157 Mr. Lindley endeavored formerly (1834) to show, in the "Fossil Flora," that Trigonocarpum Noeggerathii, a fruit found in the coal measures, has the true structure of a palm-fruit; but Ad. Brongniart has since inclined to regard it as cycadeous; nor is the French botanist satisfied that some specimens of supposed palm wood from the coal-mines of Radnitz in Bohemia, described by Corda, really belong to palms. On the other hand, Corda has proved Flabellaria borassifolia of Sternberg to be an exogenous plant, and Brongniart contends that it was allied to the Cycadeæ. See Tableau des Genres de Végétaux Fossiles. Paris, 1849.

158 Prodrome d'une Hist. des Végét. Foss. p. 179. See also a late paper, Quart. Journ. of Geol. Soc. London, 1846, in which coal-plants of Alabama, lat. 33° N., collected by the author, are identified by Mr. Bunbury with British fossil species, showing the great southern extension of this flora.

159 König, Journ. of Sci., vol. xv. p. 20. Mr. König informs me that he no longer believes any of these fossils to be tree ferns, as he at first stated, but that they agree generically with plants in our English coal-beds. The Melville Island specimens, now in the British Museum, are very obscure impressions.

160 Fossil Flora of Great Britain, by John Lindley and William Hutton, Esqrs., No. IV.

161 Fossil Flora of Great Britain, by John Lindley and William Hutton, Esqrs. No. IV.

162 Fossil Flora, No. X.

163 This has been proved by Mr. Lindley's experiments, ibid. No. XVII.

164 I have treated of this subject in my Manual of Geology, and still more fully in my Travels in N. America, vol. ii. p. 178. For a full account of the facts at present known, and the theories entertained by the most eminent geologists and botanists on this subject, see Mr. Horner's Anniversary Address to the Geological Society of London, February, 1846. Consult also Sir H. de la Beche, on the formation of rocks in South Wales, Memoirs of Geol. Survey of Great Britain, 1846, p. 1 to 296.

165 The theory proposed in this and the following chapters, to account for former fluctuations of climate at successive geological periods, agrees in every essential particular, and has indeed been reprinted almost verbatim from that published by me twenty years ago in the first edition of my Principles, 1830. It was referred to by Sir John F. W. Herschel in his Discourse on Natural Philosophy, published in 1830. In preceding works the gradual diminution of the earth's central heat was almost the only cause assigned for the acknowledged diminution of the superficial temperature of our planet.

166 We are indebted to Baron Alex. von Humboldt for having first collected together the scattered data on which he founded an approximation to a true theory of the distribution of heat over the globe. Many of these data were derived from the author's own observations, and many from the works of M. Pierre Prevost, of Genera, on the radiation of heat, and from other writers.—See Humboldt on Isothermal Lines, Mémoires d'Arcueil, tom. iii. translated in the Edin. Phil. Journ. vol. iii. July, 1820.

The map of Isothermal Lines, recently published by Humboldt and Dove (1848), supplies a large body of well-established data for such investigations, of which Mr. Hopkins has most ably availed himself in an essay "On the Causes which may have produced Changes in the earth's Superficial Temperature."—Q. Journ. Geol. Soc. 1852, p. 56.

167 Sir J. Richardson's Appendix to Sir G. Bach's Journal, 1843-1845, p. 478.

168 Malte-Brun, Phys. Geol. book xvii.

169 On Isothermal Lines, &c.

170 Rennell on Currents, p. 96. London, 1832.

173 Scoresby's Arctic Regions, vol. i. p. 208.—Dr. Latta's Observations on the Glaciers of Spitzbergen, &c. Edin. New Phil. Journ. vol. iii. p. 97.

174 Rennell on Currents, p. 95.

175 Humboldt on Isothermal Lines.

176 Journ. of Travels in S. America, &c. p. 272.

177 Darwin's travels in S. America, p. 271.

178 Mr. Hopkins raises the question whether, in South Georgia, the descent of glaciers to the margin of the sea might not have been mistaken by Capt. Cook for the descent of the snow-line to the sea level. Quart. Journ. Geol. Soc. p. 85, 1852. The great navigator is generally very accurate, and there seem to be no observations of more recent date either to confirm or invalidate his statements.

179 After all these modern discoveries, the area still unexplored, within the antarctic circle, is more than double the area of Europe. The surface of the latter contains about 2,793,000 square geographical miles. The unexplored antarctic region, as calculated for me by Mr. Gardner, in 1840, equalled about 7,620,000 square miles.

180 On icebergs in low latitudes, by Capt. Horsburgh, by whom the sketch was made. Phil. Trans. 1830.

181 Scoresby's Arctic Regions, vol. i. p. 234.

182 This follows, observes Herschel, from a very simple theorem, which may be thus stated:—"The amount of heat received by the earth from the sun, while describing any part of its orbit, is proportional to the angle described round the sun's centre." So that if the orbit be divided into two portions by a line drawn in any direction through the sun's centre, the heat received in describing the two unequal segments of the eclipse so produced will be equal. Geol. Trans. vol. iii. part. ii. p. 298; second series.

183 On Isothermal Lines.

184 A full consideration of the effect of changes in physical geography on the distribution and extinction of species is given in book iii.

185 For calculations founded on astronomical data, see Young's Nat. Phil., Lect. xlvii.; Mrs. Somerville's Connex. of Phys. Sci., sect. 14, p. 110. Laplace, endeavoring to estimate the probable depth of the sea from some of the phenomena of the tides, says of the ocean generally, "que sa profondeur moyenne est du même ordre que la hauteur moyenne des continens et des isles au-dessus de son niveau, hauteur qui ne surpasse pas mille mètres (3280 ft.)" Mec. Céleste, tom. xi. et Syst. du Monde, p. 254. The expression "du même ordre" admits in mathematical language of considerable latitude of signification, and does not mean that the depth of the water below the level of the sea corresponds exactly to the height of the land above it.

It appeared from the observations of Sir James Ross, communicated to me in 1849, by himself, and his fellow voyager, Dr. Joseph Hooker, that in latitude 15° 3' S., longitude 23° 14' W. (the island of Trinidad, the nearest land, being 486 miles distant, and bearing S. 47 W.), they sounded with a weight of 76 lbs., and 4600 fathoms of line, which ran out to the very end, without finding bottom. Here therefore in mid-ocean the depth exceeded 27,600 feet. One of the shallowest soundings ever obtained in the open sea during the same survey, struck bottom with 2677 fathoms, or 16,062 feet, latitude 33° 21' S., longitude 9° 4' E. The surveyors arrived at the conclusion, that at a moderate distance from the shore, the depth of the great ocean always exceeds 4000 feet.

During the American survey in 1849, a much greater depth, or 5700 fathoms (34,200 feet), was sounded in the Atlantic by Lieut. Walsh, without reaching the bottom, in lat. 31° 59' N., long. 58° 43' W., or between the Bermudas and the Azores. But the deepest soundings yet published were taken Oct. 30th 1852, by Capt. Henry M. Denham, R. N., who reached bottom at 7706 fathoms (46,236 feet), lat. 36° 49' S., long. 37° 6' W., the nearest land being at the mouth of the River Plate. A weight of 9 lbs. was attached to the line, which was one-tenth of an inch in diameter; the day was calm, and the line took 9 hours 24 minutes to run out. When the bottom was struck the line was raised 50 fathoms, and then allowed to run out again. It struck at the same point as before, verifying the observations. Nevertheless some experienced surveyors have remarked that the experiment would have been more satisfactory had the weight been greater. The highest summits of the Himalaya are about 28,000 feet; the Pacific, according to this sounding, is probably at some points twice as deep as the Himalaya are high.

186 Mr. Hopkins, reasoning on data furnished by Dove's Isothermal maps, has arrived at the very interesting conclusion, that both on Snowdon and the lower mountains of the West of Ireland the snow-line would descend to within 1000 feet of the sea level, and glaciers reach the sea, if we could simply assume the three following geographical changes:—

1st, The diversion of the Gulf stream from its present northerly course; 2dly, the depression of the existing land of Northern and Western Europe, to the amount of no more than 500 feet; and 3dly, a cold current from the North sweeping over the submerged area. Quart. Journ. Geol. Soc. 1852, p. 85.

187 Daniell's Meteorological Essays, p. 103.

188 Observed by J. Crawfurd, Esq.

189 In speaking of the circulation of air and water in this chapter, no allusion is made to the trade winds, or to irregularities in the direction of currents, caused by the rotary motion of the earth. These causes prevent the movements from being direct from north to south, or from south to north, but they do not affect the theory of a constant circulation.

190 See Scoreby's Arctic Regions, vol. i. p. 378.

192 This is shown by projecting a map on the horizon of London, that is to say, by supposing the eye of the observer to be placed above that city, and to see from thence one half of the globe. For it so happens that from that point, and no other, we should behold the greatest possible quantity of land; and if we are then transferred to the opposite or antipodal point, we should see the greatest possible quantity of water. (See figs. 3 and 4.) A singular fact, first pointed out by Mr. James Gardner, namely, that only one twenty-seventh part of the dry land has any land opposite to it, is intimately connected with this excess of land in one of the two hemispheres above alluded to. Thus, in fig. 3, the land shaded black in part of China answers to that portion of the extremity of South America and Tierra del Fuego which is opposite or antipodal to it, whilst the dark spots in the northern and central parts of South America represent Borneo, Sumatra, and other antipodal islands in the Eastern Archipelago. See Gardner, Geol. Soc. Proceedings, 1833, vol. i. p. 488.

193 Humboldt on Isothermal Lines

194 Humboldt, Tableaux de la Nature, tom. i. p. 112.

195 Ad. Brongniart, Consid. Générales sur la Nat. de la Végét. &c. Ann. des Sciences Nat., Nov. 1828.

196 Sir J. Richardson, Proceedings of Geol. Soc. No. 7, p. 68, March, 1828.

197 Ad. Brongniart, Consid. Générales sur la Nat. de la Végét. &c., Ann. des Sci. Nat., Nov. 1828.

198 See a Memoir on the Alps, by Professor Sedgwick and Sir Rod. Murchison, Trans. of Geol. Soc. second ser. vol. iii. accompanied by a map.

199 See Proceedings of Geol. Soc. vol. ii. p. 334.

200 It may be observed, that the facts and inferences exhibited in this map bear not merely on the theory of climate above proposed, but serve also to illustrate the views explained in the third book respecting the migration of animals and plants and the gradual extinction of species.

201 See Sir R. Murchison's Paper on the Alps, Quart. Journ. Geol. Soc. vol. v. and my Anniversary Address for 1850, ibid. vol. vi.

202 Allgemeine Literatur Zeitung, No. cxxxix. July, 1833.

203 In this estimate, the space within the antarctic circle is not taken into account: if included, it would probably add to the excess of dry land; for the late discoveries of Capt. Sir James Ross, who penetrated to lat. 78° 10' S., confirm the conjecture of Captain Cook that the accumulation of antarctic ice implies the presence of a certain quantity of terra firma. The number of square miles on the surface of the globe are 148,522,000, the part occupied by the sea being 110,849,000, and that by land, 37,673,000; so that the land is very nearly to the sea as 1 part in 4. I am informed by Mr. Gardner that, according to a rough approximation, the land between the 30° N. lat. and the pole occupies a space about equal to that of the sea, and the land between the 30° S. lat. and the antarctic circle about one-sixteenth of that zone.

204 See papers by Mr. Smith of Jordanhill, F. G. S., and the author, Proceedings Geol. Soc. No. 63, 1839, also that of Prof. E. Forbes, before cited, p. 86, note.

205 The theorem is thus stated:—"The eccentricity of the orbit varying, the total quantity of heat received by the earth from the sun in one revolution is inversely proportional to the minor axis of the orbit. The major axis is invariable, and therefore, of course, the absolute length of the year: hence it follows that the mean annual average of heat will also be in the same inverse ratio of the minor axis."—Geol. Trans. second series, vol. iii. p. 295.

206 Ann. du Bur. des Long. 1834.

207 Poisson, Théorie Mathémat. de la Chaleur, Comptes Rendus de l'Acad. des Sci., Jan. 30, 1837.

208 Quart. Journ. Geol. Soc. 1852, p. 62.

209 Proceedings Roy. Astronom. Soc. No. iii. Jan. 1840.

210 See a Memoir on the Temperature of the Terrestrial Globe, and the Planetary Spaces, Ann. de Chimie et Phys. tom. xxvii. p. 136. Oct. 1824.

211 Sir H. Davy, Consolations in Travel: Dialogue III. "The Unknown."

212 Quart. Journ. Geol. Soc. 1852.

213 Buckland's Bridgewater Treatise, p. 409.

214 Owen's Report on "British Fossil Reptiles, to Brit. Soc." 1841, p. 200.

215 Quart. Journ. Geol. Soc. No. 6, p. 96.

216 See Hitchcock's Report on Geol. of Massachusetts, and Lyell's Travels in North America, chap. 12.

217 See Manual of Geol. by the Author, index Microlestes.

218 This figure (No. 8) is from a drawing by Professor C. Prevost, published Ann. des Sci. Nat. Avril, 1825. The fossil is a lower jaw, adhering by its inner side to the slab of oolite, in which it is sunk. The form of the condyle, or posterior process of the jaw, is convex, agreeing with the mammiferous type, and is distinctly seen, an impression of it being left on the stone, although in this specimen the bone is wanting. The anterior part of the jaw has been partially broken away, so that the double fangs of the molar teeth are seen fixed in their sockets, the form of the fangs being characteristic of the mammalia. Ten molars are preserved, and the place of an eleventh is believed to be apparent. The enamel of some of the teeth is well preserved.

219 A colored figure of this small and elegant quadruped is given in the Trans. Zool. Soc. vol. ii. pl. 28. It is insectivorous, and was taken in a hollow tree, in a country abounding in ant-hills, ninety miles to the southeast of the mouth of Swan River in Australia.—It is the first living marsupial species known to have nine molar teeth in the lower jaw, and some of the teeth are widely separated from others, one of the peculiarities in the thylacotherium of Stonesfield, which at first induced M. Blainville to refer that creature to the class of reptiles.

220 This figure (No. 10) was taken from the original, formerly in Mr. Broderip's collection, and now in the British Museum. It consists of the right half of a lower jaw, of which the inner side is seen. The jaw contains seven molar teeth, one canine, and three incisors; but the end of the jaw is fractured, and traces of the alveolus of a fourth incisor are seen. With this addition, the number of teeth would agree exactly with those of a lower jaw of a didelphis. The fossil is well preserved in a slab of oolitic structure containing shells of trigoniæ and other marine remains. Two or three other similar jaws, besides those above represented, have been procured from the quarries of Stonesfield.—See Broderip, Zool. Journ. vol. ii. p. 408. Owen, Proceedings Geol. Soc., November, 1838.

221 Darwin's Journal, chap. 19. Lyell's Manual of Geol. chap. 21, p. 279.

222 Taylor's Annals of Nat. Hist. Nov. 1839.

223 See notice by the Author, and Professor Owen, Taylor's Annals of Nat. Hist. Nov. 1839.

224 See Principles of Geology, 1st ed. 1830, vol. i p. 152.

225 The first quadrumanous fossils discovered in India were observed in 1836 in the Sewalik Hills, a lower range of the Himalayan Mountains, by Lieutenants Baker and Durond, by whom their osteological characters were determined (Journ. of Asiat. Soc. of Bengal, vol. v. p. 739), and in the year following, other fossils of the same class were brought to light and described by Capt. Cantley and Dr. Falconer. These were imbedded, like the former, in tertiary strata of conglomerate, sand, marl, and clay, in the Sub-Himalayan Mountains. (Ibid. vol. v. p. 379. Nov. 1836; and vol. vi. p. 354. May, 1837.)

The Brazilian quadrumane was found, with a great many other extinct species of animals, by a Danish naturalist, Dr. Lund, between the rivers Francisco and Velhas, in 1837.

The gibbon of the South of France was found by M. Lartet in the beginning of 1837, and determined by M. de Blainville. It occurred near Auch, in the department of Gers, about forty miles west of Toulouse, in freshwater marl, limestone, and sand. They were accompanied by the remains of the mastodon, dinotherium, palæotherium, rhinoceros, gigantic sloth, and other extinct quadrupeds. (Bulletin de la Soc. Geol. de France, tom. viii. p. 92.)

The British quadrumane was discovered in 1839, by Messrs. William Colchester and Searles Wood, at Kyson, near Woodbridge, in Suffolk, and was referred by Professor Owen to the genus Macacus. (Mag. of Nat. Hist. Sept. 1839. Taylor, Annals of Nat. Hist. No. xxiii. Nov. 1839.)

226 Owen's Introduction to British Fossil Mammals, p. 46.

227 Proceedings of Acad. Nat. Sci. Philad. Dec. 9, 1851.

231 Phys. Hist. of Mankind, vol. ii. p. 594.

232 Virgil, Eclog. iv. For an account of these doctrines, see Dugald Stewart's Elements of the Philosophy of the Human Mind, vol. ii. chap. ii. sect. 4, and Prichard's Egypt. Mythol. p. 177.

235 See ch. 37, 38, 39, 41.

236 See also Manual of Geology, ch. 11, 12.

237 It has been suspected ever since the middle of the last century, that the Caspian was lower than the ocean, it being known that in Astrakhan the mercury in the barometer generally stands above thirty inches. In 1811, MM. Engelhardt and Parrot attempted to determine the exact amount of difference by a series of levellings and barometrical measurements across the isthmus at two different places near the foot of Mount Caucasus. The result of their operations led them to the opinion that the Caspian was more than 300 feet below the Black Sea. But the correctness of the observations having afterwards been called in question, M. Parrot revisited the ground in 1829 and 1830, and inferred from new levellings, that the mouth of the Don was between three and four feet lower than that of the Wolga; in other words, that the sea of Azof, which communicates with the Black Sea, was actually lower than the Caspian! Other statements, no less contradictory, having been made by other observers, the Russian government at length directed the Academy of St. Petersburg to send an expedition, in 1836, to decide the point by a trigonometrical survey, from which it appeared that the Caspian is 101 Russian, or 108 English, feet lower than the Black Sea. (For authorities, see Journ. Roy. Geograph. Soc. vol. viii. p. 135). Sir R. Murchison, however, concludes, in 1845, from the best Russian authorities, that the depression of the Caspian is only 83 feet 6 inches.

The measurements of Major Anthony Symonds, since confirmed by French authorities, make the Dead Sea to be 1200 feet below the Mediterranean.