Principles of Geology Part 78

[350] Karamania, or a brief Description of the Coast of Asia Minor, &c. London, 1817.

[351] Geog. Syst. of Herod, vol. ii. p. 107.

[352] Euterpe, XI.

[353] Journ. of Roy. Geograph. Soc. vol. ix. p. 432.

[354] Quart. Journ. Geol. Soc. vol. v.; Memoirs, p. 20; and La.s.saigue, Journ. Pharm. t. v. p. 468.

[355] Quart. Journ. Geol. Soc. 1848, vol. iv. p. 342.

[356] Flint's Geography, vol. i. p. 142. Lyell's Second Visit to the United States, vol. ii chaps. 28 to 34.

[357] Geograph. Descrip. of Louisiana, by W. Darby, Philadelphia, 1816, p. 102.

[358] Flint's Geography, vol. i. p. 152.

[359] Travels in North America, vol. iii. p. 361.

[360] Travels in North America, vol. iii. p. 362.

[361] "The boats are fitted," says Captain Hall, "with what is called a snag-chamber;--a part.i.tion formed of stout planks, which is calked, and made so effectually water-tight that the foremost end of the vessel is cut off as entirely from the rest of the hold as if it belonged to another boat. If the steam-vessel happen to run against a snag, and that a hole is made in her bow, under the surface, this chamber merely fills with water."--Travels in North America, vol. iii. p. 363.

[362] Darby's Louisiana, p. 33.

[363] Featherstonhaugh, Geol. Report, Washington, 1835, p. 84.

[364] Trees submerged in an upright position have been observed in other parts of N. America. Thus Captains Clark and Lewis found, about the year 1807, a forest of pines standing erect under water in the body of the Columbia river, which they supposed, from the appearance of the trees, to have been submerged only about twenty years. (Travels, &c. vol. ii. p.

241.) More lately (1835), the Rev. Mr. Parker observed on the same river (lat. 45 N., long. 121 W.) trees standing in their natural position in spots where the water was more than twenty feet deep. The tops of the trees had disappeared; but between high and low water-mark the trunks were only partially decayed; and the roots were seen through the clear water, spreading as they had grown in their native forest. (Tour beyond the Rocky Mountains, p. 132.) Some have inferred from these facts that a tract of land, more than twenty miles in length, must have subsided vertically; but Capt. Fremont, Dec.

1845 (Rep. of Explor. Exped. p. 195), satisfied himself that the submerged forests have been formed by immense land-slides from the mountains, which here closely shut in the river.

[365] For an account of the "sunk country," shaken by the earthquake of 1811-12, see Lyell's Second Visit to the United States, ch. 33.

[366] Darby's Louisiana, p. 103.

[367] The calculations here given were communicated to the British a.s.sociation, in a lecture which I delivered at Southampton in September, 1846. (See Athenaeum Journal, Sept.

26, 1846, and Report of British a.s.sociation, 1846, p. 117.) Dr. Riddell has since repeated his experiments on the quant.i.ty of sediment in the river at New Orleans without any material variation in the results.

Mr. Forshey, in a memoir on the Physics of the Mississippi, published in 1850, adopts Dr. Riddell's estimate for the quant.i.ty of mud, but takes 447,199 cubic feet per second as the average discharge of water for the year at Carrolton, nine miles above New Orleans, a result deduced from thirty years of observations. This being one-tenth more than I had a.s.sumed, would add a tenth to the sediment, and would diminish by one-eleventh the number of years required to accomplish the task above alluded to. "The cubic contents of sedimentary matter," says Forshey, "are equal to 4,083,333,333, and this sediment would annually cover twelve miles square one foot deep."

[368] The Mississippi is continually shifting its course in the great alluvial plain, cutting frequently to the depth of 100, and even sometimes to the depth of 250 feet. As the old channels become afterwards filled up, or in a great degree obliterated, this excavation alone must have given a considerable depth to the basin, which receives the alluvial deposit, and subsidences like those accompanying the earthquake of New Madrid in 1811-12 may have given still more depth.

[369] Account of the Ganges and Burrampooter rivers, by Major Rennell, Phil. Trans. 1781.

[370] Trans. of the Asiatic Society, vol. vii. p. 14.

[371] Cuvier referred the true crocodiles of the Ganges to a single species, _C. biporcatus_. But I learn from Dr. Falconer that there are three well-marked species, _C. biporcatus_, _C.

pal.u.s.tris_, and _C. bombifrons_. _C. bombifrons_ occurs in the northern branches of the Ganges, 1000 miles from Calcutta; _C.

biporcatus_ appears to be confined to the estuary; and _C.

pal.u.s.tris_, to range from the estuary to the central parts of Bengal. The garial is found along with _C. bombifrons_ in the north, and descends to the region of _C. biporcatus_ in the estuary.

[372] See below, ch. 22 and 29.

[373] Second Visit to the United States, vol. ii. p. 145.

[374] Asiatic Researches, vol. xvii. p. 466.

[375] Lyell's Second Visit to the United States, vol. ii.

chap. 34.

[376] See Manual of Geology by the Author.

[377] See p. 13.

[378] Geog. of Herod, vol ii. p. 331.

[379] Ibid. p. 328.

[380] Romme, Vents et Courans, vol. ii. p. 2. Rev. F. Fallows, Quart. Journ. of Science, March, 1829.

[381] The heights of these tides were given me by the late Captain Hewett, R. N.

[382] On the authority of Admiral Sir F. Beaufort, R. N.

[383] Consult the map of Currents by Capt. F. Beechy, R. N., Admiralty Manual, 1849, London.

[384] Rennell on Currents, p. 58.

[385] Rennell on the Channel current.

[386] An. du Bureau des Long. 1836.

[387] Second Parliamentary Report on Steam Communication with India, July, 1851.

[388] Phil. Trans. 1830, p. 59.

[389] See Capt. B. Hall, On Theory of Trade Winds, Fragments of Voy. second series, vol. i., and Appendix to Daniell's Meteorology.

[390] Treatise on Astronomy, chap. 3.

[391] Descrip. of Shetland Islands, p. 527, Edin. 1822, to which work I am indebted for the following representations of rocks in the Shetland Isles.

[392] Dr. Hibbert, from MSS. of Rev. George Low, of Fetlar.

[393] Hibbert, p. 528.

[394] Hibbert, p. 519.

[395] Account of Erection of Bell Rock Lighthouse, p. 163.