1864.] 



LOGAN LAURENTIAN FOSSILS. 



47 





of still older laminated sand-rock, and the 

 formation of these beds leads lis still farther 

 into the past. 



In both the Upper and Lower Laurentian 

 series there are several zones of limestone, 

 each of sufficient volume to constitute an 

 independent formation. Of these calcareous 

 masses it has been ascertained that three, at 

 least, belong to the Lower Laurentian. But 

 as we do not as yet know with certainty 

 either the base or the summit of this series, 

 these three may be conformably followed by 

 many more. Although the Lower and Upper 

 Laurentian rocks spread over more than 

 200,000 square miles in Canada, only about 

 1500 square miles have yet been fully and 



Fig. 2. — Section across Trembling 

 Mountain (21 miles). 



Upper Laurentian. 

 Fourth gneiss. 

 Third limestone. 

 Third gneiss. 



e'. Second limestone. 

 e. Second gneiss. 

 /'. First limestone. 

 /. First gneiss. 



connectedly examined in any one district, 



and it is still impossible to say whether the 



05 numerous exposures of Laurentian limestone 



met with in other parts of the province are 



1 equivalent to any of the three zones, or 

 .^ whether they overlie or underlie them all. 



_ I J In the examination of these ancient rocks, 



§ "S fl the question has often naturally occurred to 



'BU'B me whether, duiing these remote periods, or- 



!» 1-^ 1-^ ganic life had yet appeared on the earth. The 



o o Q apparent absence of fossils from the highly 



o ch^ crystalline limestones did not seem to oifer a 



. . . proof in negation, any more than their un- 



"^ discovered presence in newer crystalline 



limestones, where we have Kttle doubt they 



have been obliterated by metamorphic action ; 



while the carbon which, in the form of 



graphite, constitutes beds, or is disseminated 



through the calcareous or siliceous strata of 



