CONDUCTION AND RADIATION. 529 



any remarkable case to be a portion of the history 

 of science. We proceed to some such applications. 



Sect. 4. The Geological and Cosmological Appli- 

 cation of Thermotics. 



BY far the most important case to which conclu- 

 sions from these doctrines have been applied, is 

 that of the globe of the earth, and of those laws 

 of climate to which the modifications of tempera- 

 ture give rise ; and in this way we are led to infer- 

 ences concerning other parts of the universe. If 

 we had any means of observing these terrestrial 

 and cosmical phenomena to a sufficient extent, they 

 would be valuable facts on which we might erect 

 our theories ; and thus form part, not of the corol- 

 laries, but of the foundations of our doctrine of 

 heat. In such a case, the laws of the propagation 

 of heat, as discovered from experiments on smaller 

 bodies, would serve to explain these phenomena of 

 the universe, just as the laws of motion explain 

 the celestial movements. But since we are almost 

 entirely without any definite indications of the con- 

 dition of the other bodies in the solar system as 

 to heat ; and since, even with regard to the earth, 

 we know only the temperature of the parts at or 

 very near the surface, our knowledge of the part 

 which heat plays in the earth and the heavens 

 must be in a great measure, not a generalization 

 of observed facts, but a deduction from theoretical 



