OP VOLCAN08. 393 



volcanic phenomena are probably the result of a communication 

 either permanent or transient between the interior and exterior of 

 the globe. Elastic vapours press the molten oxidizing substances 

 upwards through deep fissures. Volcanos might thus be termed 

 intermitting springs or fountains of earthy substances j i. e. of the 

 fluid mixture of metals, alkalies, and earths which solidify into lava 

 currents and flow softly and tranquilly, when being upheaved they 

 find a passage by which to escape. In a similar manner the 

 Ancients represented (according to Plato's Phaedon) all volcanic 

 fiery currents as streams flowing from the Pyriphlegethon. 



To these considerations and views let me be permitted to add 

 another more bold. May we not find in this internal heat of our 

 globe (a heat indicated by thermometric experiments on the 

 waters of springs rising from different depths, ( 3 ) as well as by our 

 observations on volcanos) a cause which may explain one of the 

 most wonderful phenomena with which the study of fossils has 

 made us acquainted ? Tropical forms of animals, and, in the vege- 

 table kingdom, arborescent ferns, palms, and bambusaceae, are found 

 buried in the cold regions of the North. Everywhere, the Ancient 

 World shows 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 satis- 

 factory 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 favorable or un- 

 favorable harvests of particular years); I am disposed to recognize 

 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 astronomical position, various causes for the development of heat ; 

 processes of oxidation, 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 



