204 Bigsby— On the Laurentian Formation. 
0:26 of azote. Delesse states, moreover, that this azote, generally 
speaking, is not the product of infiltration, but existed in the rocks’ 
at the time of their being laid down.* 
Conclusion.—It appears, then, from the foregoing statements that 
there is in Laurentian rocks an abundance, both diffused and segre- 
gated, of the prime ingredients of organic structure,—lime, phos- 
phorus, azote, carbon, and the like. How is it that no life- forms, no 
half-consumed relics of individual existences have been met with, or 
very few, and those obscure, in the greatly varied strata of 
Laurentian age? How is it that the Lingula-flags of Wales, the 
‘Primordial Zone’ of Bohemia, the lowest beds of the Silurian of 
North America, are often full of remains of highly organized beings, 
while, if we descend the vertical scale only a few feet, there is little 
or no evidence of life? A little above us numerous groups, societies, 
and dynasties of living beings are represented, flesh-eaters and plant- 
eaters, that exercised the very functions of the present day ; here, 
however, we meet a blank, sudden and almost perfect. 
It is difficult to account for this: mere metamorphic action 
does not explain it ; for abundance of instances are known where 
strong indications of past life are seen in the midst of intense meta- 
morphism ;f and although in general the Laurentian metamorphism 
is powerful, in parts it is weaker, necessarily so in a process 
dependent for its effects on the composition of the rock it attacks. 
An active search among the beds near the conglomerates may pos- 
sibly be successful. Those who have hitherto been locking for traces 
of fossil life in rocks of this epoch may have been faint-hearted and 
unexpecting. Some have been ill-informed and unskilful ; and it is 
as true in field-geology as in other pursuits, that a man will bring 
home with him according to what he takes out. 
It now remains to add that in the Laurentians of Canada marks 
of life are supposed to have been met with in three separate places. 
The one is from a crystalline limestone of the Carrying Place of the 
Grand Calumet (River Ottawa), found by Mr. J. M‘Mullen (Canada 
Geological Commission). ‘The specimens from this place ‘ present 
parallel or apparently concentric layers resembling those of Stroma- 
topora rugosa, except that they anastomose at several points. The 
layers are composed of crystalline pyroxene, while the interstices 
are filled with crystalline carbonate of lime.’t 
Secondly, Dr. James Wilson, of Perth, some years ago found 
loose masses of limestone in the vicinity of that town (65-67 
miles SSE. from the Grand Calumet), which contain similar forms 
to those just described. ‘They are ‘composed of dark-green con- 
cretionary serpentine, while the interstices are filled with crystalline 
dolomite.’ ‘If both are to be regarded as the results,’ says Sir W. 
Logan, ‘ of unaided mineral arrangement, it would seem strange that 
identical forms should be derived from minerals of such different 
* Mémoire, p. 162. 
+ See a paper on Metamorphic yar | in the Edinb. New Phil. Journ. n.s. April, 
1863." 
+ Report Geol. Canada, 1862, p. 48. 
