[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 Diatomaceæ and Desmidiæ.