time, injured its structure. Such instances occur in 

 many places. The piuite is found at St. Pardoux, in 

 France, in a pulverulent granite, which is evidently 

 injured in its structure by some of the causes which 1 

 have mentioned ; but this, most probably, is nothing 

 more than a vein, exposed in the great mass of more 

 perfectly formed granite; and of this and the lime- 

 stone rocks en masse, I would ask, in general terms, 

 where are the instances that bear the unequivocal 

 marks of a progressive decomposition? 



Dr. Hutton would have us believe that the moun- 

 tains are in a progressive state of destruction, whilst 

 their debris are carried away by the torrents into the 

 ocean. 



Mr. Klrwan seems also to be of the opinion that 

 they are decomposing, " by being corroded by air and 

 moisture/' and hence concludes, that their summits 

 were once much higher than at present.* Yet when 

 combatting Dr. Hutton' s theory, he endeavours to 

 prove that those which are composed of granite do not 

 decay, t au( J refers to the remarks of Patrin, on the in- 

 destructibility of granite, for support. 



Pallassau makes frequent mention of the disinte- 

 gration of the rocks of the Pyrennees, which are 

 mostly of granite and limestone ; and remarks that 

 they are constantly yielding their materials, for the 

 formation and extension of the soil in the valleys be- 



* Kirwan's E&says, p. 98. 

 t Ibid, p. 436, 





