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Published online by Cambridge University Press: 01 May 2009
The Laurentian Group is as complex in its composition as the younger fossiliferous metamorphic rocks; silica, alumina, lime, and carbon compose its beds, together with phosphorus, fluor, barytes, &c.; and it develops the same accidental minerals—staurotide, garnet, pyroxenx, metallic compounds, &c. Why then should there not be in it the buried forms of life? It is found that, as we descend in the great sedimentary column, the organic remains gradually lose substance and form, until they wholly disappear, so that in the group with which we are now concerned (the very earliest we know of) not only has the original substance of the animal and its habitation vanished, but, for the most part, the very form also: and we have the residuary elements of the organisms—lime, phosphorous, &c., in masses sometimes extraordinarily large, corresponding with the extent and thickness of this great group, at least 30,000 feet in Canada (Logan), and 30,000 feet in Norway (Durocher).
Continued from p. 158.
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page 201 note ‡ DrPercy, , in his ‘Swinian Lectures’ of 1863 (Dec. 19), mentions a similar occurrences in the manufacuture, by the humid way, of carbonate of magnesia from pure dolomite (so determined by chemical analysis) —so strong and unpleasant an odour arose in the process that it had to be abandoned, as a commerical failure.Google Scholar
page 201 note § Geological Chemistry, Engl. edit. vol. ii. p. 183.Google Scholar
page 201 note ║ Observations on some points in American Geology. 1861.Google Scholar
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page 202 note † Loc. cit. p. 39.Google Scholar
page 202 note ‡ Report, 1863, p. 26.Google Scholar
page 202 note § I allude to the two following deposits of this phosphate only with the view of showing the great quantities in which it occurs almost pure. At Logrosan, near Costanoza, in Spain, phosphorite (so called) occurs in verticle layers, 2–22 feet thick, alternating with clay-slate (Silurian?) and a coarse quartz-rock. When pure it contains 81 per cent. of basic phosphate of lime. It is not worked. By far the most widely spread and continuous bed of this phosphate is that seen by Count Keyserling at the base of the White Chalk in Russia (Bull. Soc. Géol. Fr., n. s. vol. iv. p. 11); although only a few inches thick, it extends, with a varying breadth, to the distance of 550 miles.Google Scholar
page 203 note * Durocher, loc. cit. p. 37.Google Scholar
page 203 note † Bischoff, Chemical Geology, vol. ii. p. 344.Google Scholar
page 203 note ‡ Traité des Roches, p. 182.Google Scholar
page 203 note § Logan, , Geol. of Canada, 1862, pp. 26, 37.Google Scholar
page 203 note ║ Durocher, , loc. cit. p. 14.Google Scholar
page 203 note ¶ Quart. Journ. Geol. Soc., vol.xv. p. 493; Bischoff, Chem. Geol., vol. i. p. 42. Ebelmen, Bull. Soc. Géol. Fr., n. s. vol. ix. p. 223.Google Scholar
page 203 note ** Delesse, Mémoire de l' Azote, p. 17.Google Scholar
page 203 note †† Annales des Mines, 5e sér. vol.xviii. pp. 196, 308, 309, 315.Google Scholar
page 203 note ‡‡ Mémoire, pp. 170, 171.Google Scholar
page 204 note * Mémoire, p. 162.Google Scholar
page 204 note † See a paper on Metamorphic Rocks in the Edinb. New Phil. Journ. n. s. April, 1863.Google Scholar
page 204 note ‡ Report Geol. Canada, 1862, p. 48.Google Scholar
