OP VOLCANOS. 229 



experiments on the waters of springs rising from different 

 depths, ( 3 ) as well by our observations on volcanos), a 

 cause which may explain one of the most wonderful phe- 

 nomena with which the study of fosssils has made us ac- 

 quainted ? Tropical forms of animals, and, in the vegetable 

 kingdom, arborescent ferns, palms, and bambusacea?, are 

 found buried in the cold regions of the North. Everywhere 

 the ancient world shews a distribution of organic forms at 

 variance with our present climates. To resolve so important 

 a problem, recourse has been had to several hypotheses ; such 

 as the approach of a comet, a change in the obliquity of the 

 Ecliptic, and a different degree of intensity in the solar light. 

 None of these explanations are satisfactory at once to the 

 astronomer, the physicist, and the geologist. For my part 

 I willingly leave the axis of the Earth in its place, and 

 suppose no change in the light of the solar disk (from 

 whose spots a celebrated astronomer was inclined to explain 

 the favourable or unfavourable harvests of particular years) ; 

 I am disposed to recognise that in each planet there exist, 

 independently of its relations to the central body of the 

 system to which it belongs, and independently of its astro- 

 nomical position, various causes for the development of 

 heat; processes of oxydation, precipitations and chemical 

 changes in the capacity of bodies, by increase of electro- 

 magnetic intensity, and communications opened between the 

 internal and external portions of the planet. 



It may be that in the Ancient World, exhalations of heat 

 issuing forth through the many openings of the deeply 



