Dr. J. R. Mayer on Celestial Dynamics. 419 



The temperature of the crust of the globe likewise furnishes 

 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 augmented at the rate of 

 1° for every 30 metres. The same result was obtained by ob- 

 servations in the artesian well at Mondorf 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 formation of 

 springs. The water obeying the laws of gravity, percolates 

 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 tempera- 

 ture. If, however, the water in its course meets with mineral 

 or organic substances which it can dissolve and retain, 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 temperature 

 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 of the earth's crust 

 increases at the rate of 1° for every 30 metres we descend from 

 the surface towards the centre. Although it is incredible that 

 this augmentation can continue at the same rate till the centre 

 be reached, we may nevertheless assume with certainty that it 

 does continue to a considerable depth. Calculation based on 

 this assumption shows that at a depth of a few miles a tem- 

 perature must exist sufficiently powerful to fuse most substances. 

 Such molten masses penetrate the cold crust of the globe in 

 many places, and make their appearance as lava. 



A distinguished scientific man has lately expressed himself 

 on the origin of the interior heat of the earth as follows : — " No 

 one of course can explain the final causes of things. This much, 

 however, is clear to every thinking man, that there is just as 

 much reason that a body, like the earth for example, should be 

 warm, warmer than ice or human blood, as there is that it 

 should be cold or colder than the latter. A particular cause 

 for this absolute heat is as little necessary as a cause for 



