THE 



CANADIAN 



NATUEALIST AND GEOLOGIST. 



BY E. BILLINGS. 



Volume I. JANUARY, 1857. Number VI. 



ARTICLE LVI. — 0?i American Geological History: — Address 

 before tlie American Association for the Advancement of 

 Science, August, 1855, by James D. Dana.* 



( Concluded.) 



As plants may live in water too hot or impure for animals, and 

 moreover, since all nature exemplifies the principle that the earth's 

 surface was occupied with life as soon as fitted, and with the 

 highest forms the conditions of the time allowed, we may reason- 

 ably infer that there may have been in Azoic times marine species 

 and plant-infusoria forms adapted to aid in the earth's physical 

 history ; and thus vegetation may have long preceded animal life 

 on the globe.f 



* Sillimaa's American Journal of Science, November, 1856. 



f The evidence with respect to the existence of plants in the Azoic Age, 

 though by no means positive, is stronger than here stated. — In the first 

 place, there are limestones among the folded strata; and as limestones of 

 later ages were almost wholly of organic origin, these of Azoic rocks 7nay 



