Temperature of the Terrestrial Globe. 15 



this last result can be applied to all suppositions which can be made 

 upon the cause, whether it be regarded as local or universal, con- 

 stant or variable. 



When we examine all the observations relative to the figure of the 

 earth attentively, and according to principles of dynamics, we can- 

 not doubt that the earth received at its origin a very high tempera- 

 ture. On the other hand, therraometrical observations show that 

 the actual distribution of heat in the crust of the earth, is pre- 

 cisely what it would be if the earth had been formed in a medium 

 of very high temperature, and had afterwards been left gradually to 

 cool. It is important to notice the agreement of these two kinds of 

 observations. 



The question of terrestrial temperature has always appeared to us 

 as one of the most important inquiries relating to cosmogony; and 

 we have had this principally in view in establishing the mathemat- 

 ical theory of heat. From the commencement of our researches we 

 have been desirous of ascertaining the laws of internal temperature 

 in a solid sphere, heated at first by immersion in a medium, and af- 

 terwards left to cool in a medium of lower temperature. The me- 

 moir of 1807, before cited, contains a complete solution of that ques- 

 tion, which was never before examined. 



We have therefore determined the variable state of a globe, of a 

 substance whose specific qualities we know, by experiment, and 

 which after being immersed for some time in a heated medium, is 

 transported to a colder space. We have considered likewise the va- 

 riable state of a sphere which, having been plunged successively and 

 for some time in two or more media of different temperatures, should 

 undergo a final cooling in a medium of constant temperature. 



After having noticed the general consequences of the solution of 

 that question, we have examined particularly the case in which the 

 primitive temperature acquired in a heated medium, might become 

 common to the whole mass. And supposing the solid sphere to be 

 of very great dimensions, we have endeavored to ascertain the law 

 of progressive diminution of temperature in those strata nearest the 

 surface. If we apply the results of this analysis to our globe, to as- 

 certain what would be the successive effects of a primitive formation 

 like that we have just supposed : we find that the increase of a thir- 

 tieth of a degree per metre, considered as the resultant of central 

 heat, has in former periods been much greater, and that this increase 

 is now almost a constant quantity, since more than thirty thousand 



