ROW THE EARTH IS WEIGHED. 



749 



Humboldt, that the dry continental parts of the crust of the earth 

 have a mean density of from 2'4 to 2*6, and the dry and oceanic parts 

 of 1*5, and accept Reich's later estimate of the mean total density at 

 5 "58, then the inaccessible, internal parts of the earth must have a 



Fig. 4. 



Zs, 



a 



mean specific weight of 9"66. Only the metals among the bodies in 

 the accessible parts of the earth possess so great a density ; vre have 

 a right, then, to believe that the nucleus of the earth possesses a me- 

 tallic constitution. 



The density of the other heavenly bodies is deduced from that of 

 the earth, by observing the amount of attraction which two bodies 

 exert upon each other, and upon a third, and, having ascertained the 

 distances apart of the three bodies, calculating their mutual densities 

 by approved mathematical formulas. Die Xatur. 



