352 



PALEOZOIC TIME. 



2. Climate, Atmosphere. — The growth of the Carboniferous vege- 

 tation was dependent, as now, on the climate and the condition of the 

 atmosphere. 



(1.) Temperature of the Ocean and Air. — In the animal life of the 

 waters, we have a safe criterion for the temperature of the oceans. 

 Among the species, there was the large coral, Lithostrotion, common 

 in both Europe and the United States. One such species is almost 

 sufficient to prove a similar temperature for the ocean over these two 

 distant regions. This Lithostrotion was found by Beechey on the 

 northwest Arctic coast, between Point Barrow and Kotzebue Sound ; 

 and with it occurred other corals, and, among the Brachiopods, Produc- 

 tus semireticulatus, well known in lower latitudes. The Arctic was, 

 therefore, at that time a reef-growing sea ; and, if the distribution of 

 corals, forming coral-reefs, was limited by the same temperature then 

 as now, the waters were at no part of the year below 66° F. Besides 

 the above species, there have been identified, in the Arctic, the Euro- 

 pean species Productus sulcatus Sow., Atrypa aspera Dalm., A. fallax 

 Sow. These were found on Bathurst and the neighboring islands, in 

 latitudes 75° and 77°. 



The small diversity in the oceanic temperature of the globe is fur- 

 ther shown by the occurrence of the following Carboniferous species 

 in the Bolivian Andes : Productus semireticulatus, P. longispinus Sow., 

 Athyris subtilita, and a Bellerophon, resembling B. Urii Flem. 



The coal-beds of Arctic regions are evidence of a profuse growth of 

 vegetation over an extended area, and protracted through a long period. 

 The conditions, between the latitudes 70° and 78°, were, therefore, 

 analogous to those over the United States, from Pennsylvania to Ala- 

 bama, and from Illinois to Texas. While a general resemblance to the 

 ancient flora of the United States and Europe is apparent from the 

 observations which have been made, but few species have yet been 

 identified. The plants were not mosses of peat swamps, such as now 

 extend far north. If we draw any conclusion from the facts, it must 

 be that the temperature of the Arctic zone differed but little from that 

 of Europe and America. Through the whole hemisphere — and, we 

 may say, world — there was a genial atmosphere for one uniform type 

 of vegetation, and there were genial waters for Corals and Brachio- 

 pods. 



(2.) Moisture of the Atmosphere. — A warm state of the globe 

 would necessarily imply a very much larger amount of evaporation 

 than now. The climate would be insular throughout ; and heavy mists 

 would rest over the land, making the air and land moist. The com- 

 paratively small diversity of climate between the equator and poles 

 would probably be attended with fewer storms than now, and with a 

 lees rapid movement in the general circulation. 



