II 



^ 



ILLUSTRATIONS OF THE 





iiofpliere, but from this, that the wafte and de^ 



tritus to Mhich 



all things are fubjed:, will not 



allow foft and weak fubilances 



to r 



emain long 



m an expofed and elevated fituatioo ? Were it 

 iiot for this, the fecondary rocks, being in pofi- 

 tion fuperincumbent on the primary, ought to 

 be the higheft of the two, and fhould cover the 

 primary, (as they no doubt have at one time 

 done), in the hitrheft as well as the ioweft fitua- 



tions, or among the mountains as well as in the 

 plains. 



no. "Again, wherefore is it, that among all 

 mountains, remarkable for their ruggednefs and 



afperity, the rock, on examination, is always 

 found of very unequal deflmftibility, lome parts 



yielding to the weather, and to the other caufes 

 of dilintegration, much more ilowly than the 

 reft, and having ftrength fufficient to iupport 

 themfelves, when left alone, in fiender pyramids, 

 bold projedions, and overhanging cliiTs ? Where, 

 on the other hand, the rock waftes uniformly, 

 the mountains are iirailar to one another ; their 

 fwells and flopes are gentle, and they are bound- 

 ed by a waving and continuous furface. The 

 intermediate degrees of refiftance w^hich the 

 rocks oppofe to the caufes of deilrudion, produce 

 intermediate forms. It is this which gives to 

 the mountains, of every different fpecies of rock? 



/ 



