Earth's Surface during' the Tertian/ Period. 209 



which an augmentation more rapid than at the present day could 

 produce in the temperature of deep places. These accessory ef- 

 fects may, according to M. Elie de Beaumont, be reduced to 

 three, which have all concurred to render the polar climates 

 much less different from the equatorial climate than they are at 

 present. 



1 . In the more ancient geological periods, the polar ice could 

 not exist, and its absence would probably of itself be sufficient 

 to elevate the mean temperature of the pole to 0° (32° F.), 

 whereas, at the present day, it is perhaps 25° below 0° ( — 1S° F.) 



2. Since the polar ice did not exist, the sea must have pre- 

 sented, from the surface to the greatest depth, a much more 

 equal temperature than at the present day. This temperature 

 must have been every where a certain number of degrees above 

 the maximum of the density of the water of the sea. In such a 

 sea, the temperature of the surface could never be lowered more 

 than a very small quantity below the temperature of the mass. 

 This sea must have been covered by fogs in the parts near the 

 poles, whenever the sun was removed from the horizon. 



3. Since the temperature of deep places increased ten times 

 more rapidly than at the present day, thermal sources and jets 

 of hot vapour must have been much more frequent; nearly all 

 the springs must have been thermal ; and each time the sun left 

 the horizon of the poles, the surface must have been covered by 

 fogs, which prevented nocturnal radiation, and the radiation in 

 winter. These fogs, which existed only during the absence of 

 the sun, moderated the cold of the nights and the winters, with- 

 out changing the temperature of the summers. They, there- 

 fore, elevated the mean temperature, and rendered the chmate 

 more mild, more uniform, and more equatorial. They were 

 united with the action of a sea, which was warmer and more dif- 

 ficult to be cooled at the surface, to produce in the temperature 

 of the pole a positive anomaly, diametrically contrary to the ne- 

 gative anomaly produced by the permanent ice of the present 

 day. 



