Bigsby —On the Laurentian Formation. 203 
but not in the same profusion as in Canada. In the Isle of Pargas, 
near Abo, Gulf of Bothnia, it is sky-blue and green, disseminated in 
whitish marble.* 
Sulphur.—tits existence prior to animal life is doubtful. It appears 
to be derived in a free state from the animal kingdom.f It is an 
after-formation, says Coquand.{ We have it in the Laurentian rocks 
of Canada§ and Scandinavia in the sulphurets of copper, lead, and 
iron; while the Norwegian beds contain also the sulphuret of zinc, 
with the sulpharseniurets of iron and cobalt. || 
In Canada both marble and gneiss are largely charged with iron- 
pyrites, the presence of which in metamorphic rocks is inimical to 
their having been altered by great heat, unless we suppose it to 
have been brought in by subsequent infiltration. 
Iron.—According to Sterry Hunt,{ one of the most successful 
labourers in chemical geology, and as confirmed by Bischoff, Ebel- 
men, and others, the presence of iron indicates the existence of 
organic substances when the oldest metamorphic rocks were being 
deposited ; and in them the quantity in Canada, the United States, 
Norway, &c., is known to be immense. 
Azote.—The remarkable investigations of Delesse on the relations 
of azote, or nitrogen, to rock-formations and their contents have led 
to important results. It is shown by him that the proportions of 
this gas in any mineral substance indicate, within certain limits, the 
age of any fossil it contains, animal or vegetable. Delesse says that, 
all things being equal, rocks and minerals have so much less of azote 
and of organic matters according as they belong to a more and more 
ancient period. He proves that azote is nearly universal through- 
out nature, and highly influential, especially as affecting the stability 
of organic substances.** All rocks contain more or less,—among 
others, tf granite, gneiss, marble, basalt, obsidian (voleanic rocks 
usually having the least). In soils it is very plentiful. In two 
specimens of Laurentian rock,{{ one of mica, the other of black 
porphyry with crystals of labradorite, the proportion of azote was 
found to be low—0:07 and 0°10 in 1000; and a granite from the 
Vosges (probably Laurentian) gave 0°15 in 1000. This ratio is, as 
Delesse expected, from the antiquity of the rocks examined. A 
Triassic dolomite gave 0°26, and bitumen from the lake in Trinidad 
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. Soe. 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. 
* Durocher, (oc. cit. p. 37. 
f Bischoff, Chemical Geology, vol. ii. p. 344. { Traité des Roches, p. 182. 
§ Logan, Geol. of Canada, 1862, pp. 26, 37. || Durocher, oc. cit. p. 41. 
{ Quart. Journ. Geol. Soc., vol. xv. p. 498; Bischoff, Chem. Geol., vol. i. p. 42; 
Ebelmen, Bull. Soc. Géol. Fr., n.s. vol. ix. p. 223. 
** Delesse, Mémoire de l’ Azote, p. 17. 
yt Annales des Mines, 5° sér. vol. xviii. pp. 196, 808, 309, 3165. 
tt Mémoire, pp. 170, 171. 
