194 



The tendency, or liability of the several classes of 

 rocks to decomposition, in a greater or less degree, ac- 

 cording to their character and structure, is a subject, 

 of itself, highly important, and sufficiently ample, if 

 properly treated, for a copious volume. But it is not 

 consistent with the plan of this work, nor the views 

 with which 1 set out, to enter into a minute examina- 

 tion of facts and opinions on this extensive and in- 

 teresting topick. 



1 shall therefore content myself with endeavouring, 

 by a few cursory observations and remarks, to prove 

 that the decomposition of rocks is not a process so 

 general and so rapid as many seem disposed to be- 

 lieve. 



One of the principal circumstances that gave rise to 

 the opinion, that our mountains are daily crumbling 

 into dust, is, in part, the peculiar tendency of some 

 imperfectly formed rocks to fall into decay ; but more 

 particularly, the amazing quantity of alluvial de- 

 posites that have, in time, accumulated at the mouths 

 of numerous rivers ; and which, it is believed, are 

 made up of the debris of decomposed rocks which 

 have been washed by rains into creeks, thence into 

 rivers, and by the rivers wafted to the sea and de- 

 posited. 



It is from this that Herodotus, Pliny and Aristotle, 

 drew the inference, that Egypt was entirely the gift of 

 the Nile. 



