ascend the cone on foot.

[534] Dufranoy, Mam. pour servir a une Descrip. Geol. de la
France, tom. iv. p. 294.

[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 degrees instead of
30 degrees, 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] Dufranoy, Mam. 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 classes 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 shores of the
island of Cephalonia in the Mediterranean (Proceedings, Geol.
Soc. vol