436 Dr. Mac Culloch on the Geology of 



The bed of limestone has been quarried near the eastern end of 

 •the lake, and if the reports of the quarry-men are to be trusted, 

 extends in a direct line for many miles. This part of its history 

 merits investigation, as the limestones which lie in the highland 

 schistus, are generally of very limited extent. The stone itself is 

 remarkable for containing hornblende. The sides of the bed are in 

 contact with hornblende slate, or rather with that unnamed and 

 common rock, consisting of a slaty mixture of quartz, mica, and 

 hornblende. 



Where the limestone com.es in contact with the schist, the 

 hornblende crystals penetrate it in such quantity as to blacken the 

 compound. Towards the centre of the mass they diminish in 

 number, and at length disappear. 



Mica also accompanies the hornblende to a certain extent within 

 the bed, and the limestone being itself of a pure white, a marble 

 is thus produced of an ornamental nature, and bearing a consider- 

 able resemblance, as well as analogy, to the celebrated marble of 

 Tirey. A substance very much resembling massive garnet may be 

 perceived here and there united with it, but in so small a quantity 

 as to render the determination of its true nature difficult. It is 

 worthy of notice, that the limestone is frequently of a large platy 

 fracture where in contact with the hornblende schistus, and that 

 these plates are not straight but flexuous. 



Craig Cailleach near Kill'in. 



This summit forms a part of the ridge separating the vales of 

 the Tay, and Lyon, and is the next highest In elevation to Ben 

 Lawers, the most conspicuous part of that ridge. Tlie predominant 

 rock of this ridge, is a very well characterized chlorite slate, which 



