THE 



POPULAR SCIENCE 

 MONTH LY. 



JULY, 1880. 



THE INTERIOR OF THE EARTH * 



Br R. EADAU. 



THE additions that are being continually made to our knowledge 

 of the composition and physical condition of the most distant 

 heavenly bodies may well prompt one to ask why we are still so poorly 

 informed concerning the constitution of the planet which the Creator 

 has assigned to us for a dwelling-place. Mines and wells have barely 

 scratched the solid crust that conceals the mysteries of the earth's 

 depths. Our vague and uncertain ideas regarding the condition of 

 the interior of the earth are based on analogies and inductions from 

 facts observed on its surface or in the heavens. Very little light do 

 we get on this subject from direct experiment. The bowels of the 

 earth are not, indeed, easily accessible. Whatever the poet may say, 

 the descensus Averni is not easily made ; the domain of the stars is 

 not thus hidden from us. For about two centuries large sums have 

 been expended in the construction of gigantic telescopes with which 

 to sound the depths of space ; but no attempt, as a purely scientific 

 undertaking, has been made to fathom the secrets of the underground 

 world. The object of the numerous mines in different parts of the 

 world has been simply the discovery of mineral riches, and the depths 

 they have reached barely exceed, even in a few rare instances, a thou- 

 sand metres ; i. e., hardly the six-thousandth of the earth's radius 

 corresponding, on a globe thirteen metres f (about forty-two feet) in 

 diameter, to a puncture one millimetre (about four one-hundredths of 

 an inch) in depth. 



Notwithstanding this paucity of positive data, it will not be unin- 



* Translated from the "Revue des Deux Mondes," by GuyB. Seely. 

 f The length of a metre is about three feet three inches. 



VOL. XVII. 19 



