272 Dr. Mac CuLLOCH on the Geology of Glen Tilt. 



as to admit of the conversion of its siliceous layers into the substance 

 now found interstratified in the limestone, while this latter resisting 

 as it is vv'ell known to do, any change from the application of heat 

 under such circumstances, might undergo no other affection than 

 that softening which has led to its flexure and contortion. 



The remaining appearances to be seen at this rock are more cu- 

 rious as adding to the unexampled confusion of the whole mass, 

 than as offering any thing very new to the geologist in addition to 

 that which has been already detailed. 



Among the remaining substances entangled in this confusion, a 

 large vein of felspar is the most remarkable. Its course is not long, 

 nor does it appear to have any connection with the granite. It varies 

 in colour through this limited extent, being sometimes white, at 

 other times of a pink or dead lilac hue, and in some few places 

 greenish. This latter colour seems to proceed from a mixture of 

 epidote, which mineral is found in other parts of the rock in thin 

 veins accompanying the granite and colouring the schist. Some 

 massive garnet is also to be seen involved among the other substances, 

 and it seems principally connected with the limestone. In a few 

 cavities there occur crystals of flesh coloured calcareous spar, but so 

 incomplete from the narrowness of the spaces in which they have 

 crystallized, that I could not assign their figure. This I believe 

 completes the catalogue of the minerals found in this singular place. 



The granite is again seen crossing the river between this bridge 

 and Forest Lodge, and near it lies a body of quartz rock which is 

 evidently a continuation of some beds which may be observed in the 

 hill above. 



About 300 yards below the Lodge it crosses the stream again, and 

 here the limestone is again mixed with it. A set of beds of a yel- 

 lowish and greyish colour, resembling some varieties of foreign 



