384 THE CRUST OF THE EARTH. 



which pierces through the superincumbent strata, and 

 in so doing, flexes them into various shapes upon its 

 external slopes : and that the probabilities also are that 

 each of the great mountain chains of the world is 

 created by a more or less simultaneous movement of 

 the earth along the main axis of its elevation. 



The vastness of this operation may cause the minds 

 of some to stagger at the contemplation of it, but it 

 must be borne in mind how small is the proportion 

 which even the mightiest mountain range bears to the 

 whole bulk of the globe. Thus according to Herschel 

 "the earth contains 259,373 millions of cubic miles " 

 of matter, * and the bulk of what is known as the crust 

 of the earth is estimated by Mr. Mellard Reade, C.E., 

 as equal to only about -^-g^^ P art f ^ at f tne wn l e 

 globe. The crust of the earth has thus aptly been 

 described as bearing a proportion to the earth itself 

 somewhat as the rind of an orange does to the entire 

 fruit ; and the proportion borne by mountains, compared 

 with the earth's crust is so minute that Sir John 

 Herschel likens it 



" to the roughness on the rind of an orange, compared 

 with its general mass. The comparison (he states) is quite 

 free from exaggeration, because the highest known mountain 

 hardly exceeds 5 miles in perpendicular height. This (Sir 

 John Herschel points out) is only one i6ooth part of the 

 earth's diameter, consequently on a globe 16 inches in diameter 

 such a mountain would be represented by a protuberance of 

 no more than one hundredth part of an inch, which is about 

 the thickness of ordinary drawing paper. " f 



* Outlines of Astronomy, by Sir John Herschel, New Edition of 1 88 1, 

 p. 560. 



j- Ibid., p. 23. 



