740] See Proceedings of Geol. Soc. No. 42, p. 208. I also
conversed with Dr. Pingel on the subject at Copenhagen in
1834.

[741] Keilhau, Bulletin de la Soc. Gaol de France, tom. vii.
p. 18.

[742] Illust. of Hutt. Theory, Section 435-443.

[743] Herschel's Astronomy, chap. iii.

[744] See Hennessy, On Changes in Earth's Figure, &c. Journ.
Geol. Soc. Dublin, 1849; and Proc. Roy. Irish Acad. vol. iv.
p. 337.

[745] Young's Lectures, and Mrs. Somerville's Connection of
the Physical Sciences, p. 90.

[746] Phil. Trans. 1839, and Researches in Physical Geology,
1st, 2d, and 3d series, London, 1839-1842; also on Phenomena
and Theory of Volcanoes, Report Brit. Assoc. 1847.

[747] Ed. Journ. of Sci. April, 1832.

[748] Cordier, Mam. de l'Instit. tom. vii.

[749] Pog. Ann. tom. xv. p. 159.

[750] See M. Cordier's Memoir on the Temperature of the
Interior of the Earth, read to the Academy of Sciences, 4th
June, 1827.--Edin. New Phil. Journal, No. viii. p. 273.

[751] Cordier, Mam. de l'Instit. tom. vii.

[752] Phil. Mag. and Ann. Feb. 1830.

[753] The heat was measured in Wedgwood's pyrometer by the
contraction of pure clay, which is reduced in volume when
heated, first by the loss of its water of combination, and
afterwards, on the application of more intense heat, by
incipient vitrification. The expansion of platina is the test
employed by Mr. Daniell in his pyrometer, and this has been
found to yield uniform and constant results, such as are in
perfect harmony with conclusions drawn from various other
independent sources. The instrument for which the author
received the Rumford Medal from the Royal Society, in 1833, is
described in the Phil. Trans. 1830, part ii., and 1831, part
ii.

[754] The above remarks are reprinted verbatim from my third
edition, May, 1834. A memoir was afterwards communicated by M.
Poisson to the Academy of Sciences, January, 1837, on the
solid parts of the globe, containing an epitome of a work
entitled "Thaorie Mathamatique de la Chaleur," published in
1835. In this memoir he controverts the doctrine of the high
temperature of a central fluid on similar grounds to those
above stated. He imagines, that if the globe ever passed from