IV. Observations on the Mountain Cruachan in Argyleshire, 

 with some Remarks on the surrounding Country, 



By J. M ac Culloch, M.D. P.L.S. President of the Geological Society, 

 Chemist to the Ordnance, Lecturer on Chemistry at the Royal 

 Military Academy, and Geologist to the Trigonometrical Survey. 



[Read 2d December, 1814.] 



J_ HE geological history of this mountain being, as far as I know, 

 unrecorded, I shall relate the few observations which I made on it, 

 as they are sufficiently numerous to form at least a basis for future 

 and more accurate investigation. 



It is evident to any eye in approaching through the vales of 

 Glenorchy or Glenara to the head of Loch Awe, that the nature of 

 the country has changed. The rugged forms and rocky faces cha- 

 racterizing those hills of mica slate which bound Loch Lomond, 

 Loch Long, Loch Fyne, or Strath Fillan, have disappeared j the 

 mountains assume a more uniform flowing line, their sides are more 

 completely covered with herbage, and exhibit fewer denuded rocks ; 

 their summits are less serrated, and are almost the only parts which 

 exhibit the naked rock, while at the same time they are strewed with 

 heaps of fragments, a character from which the hills of mica slate 

 are almost always free. On approaching nearer to their bases, the 

 red colour of the fragments which have fallen down from their sides, 

 and the rounded pebbles of granite and porphyry which are met 

 with in the beds of the torrents, give the mineralogist pretty plain 

 intimation of the causes of this change of feature. 

 Vol. iv. q 



