262 Dr. Mac Culloch on the Geology ofCien Tilt. 



Occasionally it may be seen cutting its way through quartz rock, 

 through schist, and, not long before its arrival at the Tarff, 

 through beds of dark bluish limestone. One solitary portion of 

 pure white limestone or marble is also visible in this part of its 

 course. Where it joins the Tarff it also receives another stream of 

 considerable magnitude, flowing from Glen More and collecting the 

 waters from a set of vallies that lie between the foot of Carn-ree 

 and the head of Glen Fernat, as well as from those corys of Ben 

 Gloe which tend in this direction. 



It will be unnecessary to particularize the several streams which it 

 receives during its course to the Garry, unless where their sections 

 offer material information respecting the structure of the neighbour- 

 ing hills. 



Having passed the Tarff it begins to run in a.more rocky channel, 

 and though often, and for considerable spaces, its true bed is con- 

 cealed by the alluvial matter which it has accumulated, enough 

 remains exposed to excite the curiosity, and employ no small 

 portion of the time of a geologist. Although in enumerating and 

 describing these several points where the natural bed is visible, 

 I have used all my endeavours to specify the particular places 

 where they occur, yet in this respect the description will still be 

 deficient. Even if an accurate survey of the ground were made, 

 the want of points of reference in a valley which possesses so few 

 permanent marks for distances, would prevent me from referring to 

 them as accurately as would be desired by those who might wish to 

 follow the same track. The difhcult nature of the banks, and the 

 many inaccessible points which the river possesses, combined with 

 t^.e dangerous violence of its waters, frequently also deny access, 

 and may consequently have led to omissions. Such omissions will 

 also be found to arise from another cause, to which may equally be 



