130 Dr. Mac Culloch's observations 



a tract far removed, yet possibly not unconnected with this, is also 

 composed of granite ; and among this are found perfect granitic 

 conglomerates, in which fragments of mica schist, equalling in 

 quantity the substance which connects them, are seen imbedded 

 in a paste of granite. 



Occasionally the fragments are confounded with the mass at their 

 edges, but at times they are so denned, and even so separable, that 

 I procured a specimen with the distinct vacant impression of a rec- 

 tangular fragment which had probably been detached. Cavities left 

 in this way by the wearing out of the schist occur frequently in the 

 rocks throughout the moor of Rannoch. The union between 

 granite and the schists which it touches when passing through 

 them in the form of veins, is known to be subject to similar 

 variations. I may here add that the same appearances, though 

 more rarely, may be found in Mar, and in the granite which occurs 

 near Comrie. 



It is well known that the passage of granite veins through schist 

 is commonly well denned, and that the two are generally easily se- 

 parable by the action of the weather. But the district of Rannoch 

 offers a multiplicity of veins which are so confounded with each 

 other and with the rocks which they traverse, that their appearances 

 cannot be described. They frequently vanish so imperceptibly both 

 in the quartz rock and the mica slate, that a perfect passage from the 

 one to the other is visible, while the accessions of additional veins, 

 traversing and often shifting the already intricate structure, increase 

 the unexampled confusion which reigns among them. The granite 

 is often found imbedded in detached lumps in the schist, and I 

 must remark of these lumps and veins, however minute they may 

 be, that contrary to the granite veins and detached masses of Glen 

 Tilt or Corpach, their character is perfect even to the minutest division. 



