302 CELESTIAL DYNAMICS. 



elude that the earth at the time it received its rotatory motion 

 was in a liquid state ; and, after much controversy, it may be 

 considered as settled that this liquid condition was not that of 

 an aqueous solution, but of a mass melted by a high tempera- 

 ture. 



The temperature of the crust of the globe likewise fur- 

 nishes proof of the existence of a store of heat in its interior. 

 Many exact experiments and measurements show that the 

 temperature of the earth increases with the depth to which 

 we penetrate. In boring the artesian well at Grenelle, which 

 is 546 metres deep, it was observed that the temperature aug- 

 mented at the rate of 1 for every 30 metres. The same re- 

 sult was obtained by observations in the artesian well at Mon- 

 dorf in Luxembourg : this well is 671 metres in depth, and 

 its water 34 warm. 



Thermal springs furnish a striking proof of the high tem- 

 perature existing in the interior of the earth. Scientific men 

 are agreed that the aqueous deposits from the atmosphere, 

 rain, hail, dew, and snow, are the sole causes of the forma- 

 tion of springs. The water obeying the laws of gravity, per- 

 colates through the earth wherever it can, and reappears at 

 the surface in places of a lower situation. When water sinks 

 to considerable depths through vertical crevices in the rocks, 

 it acquires the temperature of the surrounding strata, and 

 returns as a thermal spring to the surface. 



Such waters are frequently distinguished from the water 

 of ordinary springs merely by their possessing a higher tem- 

 perature. If, however, the water in its course meets with 

 mineral or organic substances which it can dissolve and re- 

 tain, it then reappears as a mineral spring. Examples of 

 such are met with at Aachen, Carlsbad, &c. 



In a far more decided manner than by the high tempera- 

 ture of the water of certain springs, the interior heat of our 

 globe is made manifest by those fiery fluid masses which 

 sometimes rise from considerable depths. The temperature 



