204: Report of the State Geologist. 



Climate of the Silurian and the Devonian. — Since the epoch o^ 

 the Cambrian we can distinguish in Europe, as demonstrated bj 

 Barrande, two different zones — a northern and a southern ; the 

 fauna is almost identical in Russia, in Scandinavia, as well as in 

 the regions farther toward the south, such as southern Poland, 

 Galicia, Thuringia and England ; a distinct fauna is found in the 

 Montague Noire, in Sardinia, in Spain and in Portugal. This 

 second facies is identical with that of Bohemia. The same 

 genera are represented in the two bands; buc the species differ. 

 In America, where the Cambrian covers considerable areas, in 

 Siberia, in China, the northern facies alone has so far been 

 discovered. 



These facts prove incontestablj the existence of climatic zones 

 at the most remote epochs ; to undertake to explain them by the 

 existence of natural barriers is to carry back the problem with- 

 out explaining it, for if the fauna possessed this difference during 

 the Cambrian, it is because it acquired the difference from the 

 Precambrian, and it is at that time that the temperature would 

 have exercised its influence. 



It is probable that the climate was warm at the beginning of 

 the Palaeozoic epoch. This seems to be proved by the existence of 

 coral reefs which make their appearance after the Middle Silurian, 

 and which are particularly abundant in the upper part of the 

 stage, in Gotland, in the Baltic provinces of Russia, in the United 

 States and in Canada. The groups which form the present reefs 

 had not yet appeared; in their place we find Tetracorallia, Favo- 

 sitids and Stromatoporas. It would be somewhat hazardous to 

 suppose that these forms required precisely the same conditions 

 of temperature as do those of the present ; but the other conditions 

 of depth and purity of water appear to have been palpably the 

 same. 



At the Devonian epoch we find again two facies ; the ordinary 

 marine facies and a northern facies, the Old Red Sandstone, which 

 characterizes the north of England, Scotland and to some 

 degree the northern part of America. But here other consid- 

 erations besides that of temperature must intervene; the Old 

 Red Sandstone presents the character of a coastal or interior 

 basin deposit, which forbids our insisting here on points as yet 

 obscure. 



We may add that the corals of the Devonian are found also in 

 very high latitudes ; in the Ardennes, Eifel, Canada and the 

 State of New York. 



Climate of the Carboniferous epoch. — At the Carboniferous 

 epoch a new factor makes its appearance The terrestrial flora, 

 which has already representatives in the Devonian, assumes an 

 importance which warrants our introducing it into our present 

 argument. 



It is known that the geographic distribution of plants is strictly 

 related to the divisions of the climatic zones. But the area of 



