THE EAETH'S INTEKIOK HEAT. 315 



tered in many places circumstances which would doubtless 

 affect the climate in many parts of the world. Especially it 

 may be presumed that "Western Europe, with its present fa- 

 vourable climate, would become colder, and thus perhaps the 

 seat of the power and culture of our race transferred to the 

 milder parts of North America. 



Be this as it may, for thousands of years to come we can 

 predict no diminution of the temperature of the surface of 

 our globe as a consequence of the cooling of its interior mass ; 

 and, as far as historic records teach, the climates, the tempe- 

 ratures of thermal springs, and the intensity and frequency 

 of volcanic eruptions are now the same as they were in the 

 far past. 



It was different in prehistoric times, when for centuries 

 the earth's surface was heated by internal fire, when mam- 

 moths lived in the now uninhabitable polar regions, and when 

 the tree-ferns and the tropical shell-fish whose fossil remains 

 are now especially preserved in the coal-formation were at 

 home in all parts of the world. 



