THE KUUNDATK^NS OK THE CONTINENTS 95 



be observed that an immense area in Canada 

 appears to be occupied by these graphitic and 

 Eozoon hmestones, and that rich j^raphitic deposits 

 exist in the continuation of this system in the State 

 of New York ; while in rocks believed to be of 

 this age near St. John, New Brunswick, there is a 

 very thick bed of graphitic Hmestone, and associ- 

 ated with it three rcguhir beds of graphite, having 

 an aggregate thickness of about five feet.* 



" It may fairly be assumed that in the present 

 world, and in those geological periods with whose 

 orcranic remains we are more familiar than with 

 those of the Laurentian, there is no other source of 

 unoxidized carbon in rocks than that furnished by 

 organic matter, and that this has obtained its car- 

 bon in all cases, in the first instance, from the 

 deoxidation of carbonic acid by living plants. No 

 other source of carbon can, I believe, be imagined 

 in the Laurentian period. We may, however, sup- 

 pose either that the graphitic matter of the Lauren- 

 tian has been accumulated in beds like those of 

 coal, or that it has consisted of diffused bituminous 



' Matthew, in Quart. Joiirn. Geol. Soc, vol. xxi. p. 423. 

 "Acadian Geology," p. 662, 



