Principles of Geology Part 82

[535] Descrip. Phys. des Iles Canaries, p. 344.

[536] See Daubeny's Volcanoes, p. 400.

[537] Geol. of American Explor. Exped. p. 359, note. Mr. Dana informed me (Sept. 1852), that an angle of 60 instead of 30, was given by mistake in his work.

[538] Ibid. p. 354.

[539] Geol. Trans. 2d series, vol. ii. p. 341.

[540] See a paper by the Author on "Craters of Denudation,"

Quart. Journ. Geol. Soc. 1850.

[541] Dufrenoy, Mem. pour servir, &c. tom. iv. p. 285.

[542] Journal of Science, vol. xv. p. 177.

[543] Voy. dans la Campanie, tome i. p. 201.

[544] Mr. Forbes, Edin. Journ. of Sci. No. xviii. Oct. 1828.

[545] Daubeny on Volcanoes, p. 169.

[546] Scrope, Geol. Trans. second series, vol. ii. p. 346.

[547] Monticelli and Covelli, Prodrom. della Mineral. Vesuv.

[548] The great eruption, in 1822, caused a covering only a few inches thick on Pompeii. Several feet are mentioned by Prof. J. D. Forbes.--Ed. Journ. of Science, No. xix. p. 181, Jan. 1829. But he must have measured in spots where it had drifted. The dust and ashes were five feet thick at the top of the crater, and decreased gradually to ten inches at Torre del Annunziata. The size and weight of the ejected fragments diminished very regularly in the same continuous stratum, as the distance from the centre of projection was greater.

[549] Forbes, Ed. Journ. of Sci. No. xix. p. 130, Jan. 1829.

[550] Scrope, Geol. Trans. second series, vol. ii. p. 346.

[551] Napoli, 1816.

[552] Not a few of the organic bodies, called by Ehrenberg "infusoria," such as Galionella and Bacillaria, have been recently claimed by many botanists as belonging to the vegetable kingdom, and are referred to the cla.s.ses called Diatomaceae and Desmidiae.

[553] See Ehrenberg, Proceedings (Berichte) of the Royal Acad.

of Sci. Berlin, 1844, 1845, and an excellent abstract of his papers by Mr. Ansted in the Quart. Journ. of the Geol. Soc.

London, No. 7, Aug. 1846. In regard to marine infusoria found in volcanic tuff; it is well known that on the sh.o.r.es of the island of Cephalonia in the Mediterranean (Proceedings, Geol.

Soc. vol. ii. p. 220), there is a cavity in the rock, into which the sea has been flowing for ages, and many others doubtless exist in the leaky bottom of the ocean. The marine current has been rushing in for many years, and as the infusoria inhabiting the waters of the Mediterranean are exceedingly abundant, a vast store of their cases may acc.u.mulate in submarine caverns (the water, perhaps, being converted into steam, and so escaping upwards), and they may then be cast up again to furnish the materials of volcanic tuff, should an eruption occur like that which produced Graham Island, off the coast of Sicily, in 1831.

[554] Hamilton, Observ. on Mount Vesuvius, p. 94. London, 1774.

[555] Swinburne and Lalande. Paderni, Phil. Trans. 1758, vol.

i. p. 619.

[556] Prof. J. D. Forbes, Edin. Journ. of Sci. No. xix. p.

130, Jan. 1829.

[557] In one of the ma.n.u.scripts which was in the hands of the interpreters when I visited the museum in 1828, the author indulges in the speculation that all the Homeric personages were allegorical--that Agamemnon was the ether, Achilles the sun, Helen the earth, Paris the air, Hector the moon, &c.

[558] Sir H. Davy, Consolations in Travel, p. 66.

[559] Forsyth's Italy, vol. ii.

[560] In 1815, Captain Smyth ascertained, trigonometrically, that the height of Etna was 10,874 feet. The Catanians, disappointed that their mountain had lost nearly 2000 feet of the height a.s.signed to it by Recupero, refused to acquiesce in the decision. Afterwards, in 1824, Sir J. Herschel, not being aware of Captain Smyth's conclusions, determined by careful barometrical measurement that the height was 10,872 feet.

This singular agreement of results so differently obtained was spoken of by Herschel as "a happy accident;" but Dr. Wollaston remarked that "it was one of those accidents which would not have happened to two fools."

[561] Book iii. at the end.

[562] The hill which I have here introduced was called by my guide Vampolara, but the name given in the text is the nearest to this which I find in Gemmellaro's Catalogue of Minor Cones.

[563] Mem. pour servir, &c. tom. iv. p. 116.

[564] See Prof. J. D. Forbes, Phil. Trans. 1846, p. 155, on Velocity of Lava.

[565] Ferrara, Descriz. dell' Etna, p. 108.

[566] Ferrara, Descriz. dell' Etna. Palermo, 1818.

[567] This view is taken from a sketch made by Mr. James Bridges, corrected after comparison with several sketches of my own.

[568] Scrope on Volcanoes, p. 153.

[569] This drawing is part of a panoramic sketch which I made from the summit of the cone, December 1, 1828, when every part of Etna was free from clouds except the Val del Bove. The small cone, and the crater nearest the foreground, were among those formed during the eruptions of 1810 and 1811.

[570] Scrope on Volcanoes, p. 102.

[571] Ferara, Descriz. dell' Etna, p. 116.

[572] Mr. Nasmyth, the inventor of the steam-hammer, has lately ill.u.s.trated, by a very striking experiment, the non-conductibility of a thin layer of dry sand and clay. Into a caldron of iron one-fourth of an inch thick, lined with sand and clay five-eighths of an inch thick, he poured eight tons of melted iron at a white heat. After the fused metal had been twenty minutes in the caldron the palm of the hand could be applied to the outside without inconvenience, and after forty minutes there was not heat enough to singe writing-paper. This fact may help us to explain how strata in contact with dikes, or beds of fused matter, have sometimes escaped without perceptible alteration by heat.

[573] Journ. of Roy. Geograph. Soc. vol. i. p. 64.

[574] Hoffman, Geognost. Beobachtungen, p. 701. Berlin, 1839.

[575] Mem. pour servir, &c., tom. iv. Paris, 1838.

[576] Geognost. Beobachtungen, &c. Berlin, 1839.

[577] De Beaumont, Mem. pour servir, &c. tom. iv. pp. 187, 188.

[578] Mem. pour servir, tom. iv. p. 149.

[579] P. 62, _supra_.

[580] See p. 366.

[581] On the Longevity of Trees, Bibliot. Univ., May, 1831.