PALEOZOIC TIME — CARBONIC. 711 



little too much emergence, even if only a few hundred feet, there Avould 

 have been no marshes in North America; for the land would have been 

 drained. And with a little too much submergence, limestones or barren 

 sediments of sand or gravel would have covered the region. North America 

 was admirably arranged and poised for the grand result. South America 

 probably lay a little too low, and vast plains, although situated just like 

 those of Xorth America, were left barren. Europe was not so well off as 

 North America, because of the less extent of the level land surface, and 

 the consequently less equable system of oscillations. Moreover, the lands of 

 North America were on the wet border of the Atlantic, the western; and 

 those of Europe, as at the present time, on the dry border, the two differ- 

 ing now a fourth in amount of precipitation. 



METEOROLOGICAL CONDITIONS OF THE CARBONIC ERA. 



1. Temperature of the air and waters. — Using the facts from the rela- 

 tions of existing plants to climate, — that Eerns and Lycopods thrive best in 

 tropical and temperate latitudes, and Equiseta in temperate, — it is inferred 

 from the occurrence of coal-plants of each of these groups in all latitudes to 

 the Arctic regions that the climate of the globe in the Carbonic era was no- 

 where colder than the modern temperate zone, or below a mean temperature 

 of 60° F. Similarly, the occurrence in Spitzbergen of Corals of the genera 

 Lithostrotion, Cyatliophyllum, and Syringopora, and of some species of Brach- 

 iopods of twice the size they have in Europe, seems to show that the waters 

 of the ocean were equally temperate throughout. As to excessive heat in the 

 tropics, we have no evidence, since the common Carboniferous Brachiopods, 

 Productus semireticidatus, P. longispinus, Athyris subtilita, and a Bellerophon 

 near B. Urii are found in the Bolivian Andes. 



2. Hygrometric conditions. — With the atmosphere so genial and the ocean 

 so warm, evaporation would have been excessive, rains abundant, and mists 

 almost perpetual. Over the land on the favored side of the ocean, from the 

 tropics to the higher temperate latitudes, atmospheric moisture would have 

 reached its maximum. The great tropical Atlantic current — a part of the 

 world's machinery from the beginning of oceans and continents — would 

 have given moisture freely to the British Isles, more so than to Europe, and 

 more to Spitzbergen than to Greenland and the western Arctic lands. More- 

 over, Lycopods, Equiseta and most Ferns like shady as well as moist places. 



3. Influence of the carbonic acid and moisture of the atmosphere. — If the 

 amount of carbonic acid used up in the making of Subcarboniferous and later 

 limestones, and of coal and other carbonaceous products stored in the 

 rocks of the Carbonic era, could be ascertained, the amount of carbonic acid 

 abstracted from the atmosphere by the rock-making and coal-making of the 

 era would be known. In view of the facts it is safe to say that the amount 

 of carbonic acid in the atmosphere at the beginning of the era was at the 

 least 3 in 1000 parts instead of 3 in 10,000, as it is now. (See page 485.) 



