638 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



lous mass. 2d. The earth has never existed without a solid sur- 

 face. 3d. It isn't cooling, since it isn't contracting. 4th. The 

 changes in climate of different portions of the earth are due to the 

 upheaval and depression of the land. 5th. That Plutonic rocks are 

 not the oldest geological formations, and were not, therefore, the 

 lirst solid crust of our globe. 6th. That earthquakes, volcanic 

 eruptions, geysers, hot springs and Plutonic rocks are produced 

 from internal seas or lakes of the substances wherewith they are 

 composed ; that the movements of the latter are probably caused 

 by the gradual depression of the districts wherein they are located ; 

 and their formation, possibh^ by the gradual upheaval of others. 

 7th. That the earth always has been an oblate spheroid. 



The increased temperatui-e of the earth, as we descend into its 

 depths, is the only fact not yet considered. Its truth is unques- 

 tionable, but the deduction therefrom, that beyond a given depth 

 the earth must be a liquid mass, is fallacious; the fallacy lies in the 

 assumption, that an increase of temperature necessarily produces 

 expaubion. 



A substance can be heated in two ways, either under a constant 

 pressure, or a constant volume. When heated under a constant 

 volume, an increased pressure must be created for every increase 

 of temperature ; and vice versa, a body will exist at a constant 

 volume, or in other words will not expand, although different parts 

 are of different temperatures, provided the pressures upon these 

 different parts correspond with their temperatures. 



I have no dou])t that there are masses in the earth whose tempe- 

 rature is so great that they, under the pi-essure of the atmosphere 

 onlf/, would flash into vapor; but under the pressure of miles on 

 miles of earth above them, are as solid as the surface on which we 

 tread. 



The relationship between temperature and pressure cannot be 

 too forcibly urged. Water will boil under the pressure of the 

 atmosphei-e at 100° C. ; but under a pressure of atmospheres at 

 100 X Q°C. So the substances composing the earth would all melt 

 at temperatures less than 2,000° C, under the pressure of the 

 atmosphere, Imt not by any means under ten times that pressure. 



Whether the earth is entirely solid, the sources of volcanoes, 

 &c., excepted, is a question Avhose ansAver depends on the relative 

 increase of the temperature and pressure in the earth's interior. 

 If the two correspond, then the earth is solid. 



Since the internal heat of the earth is not caused by the cooling 



