576 MULL. GEOLOGY. 



a distinction, but I know not that any proofs of it have 

 yet been produced. In the composition of the substances 

 there is often but little difference ; or at least, every variety 

 is in some place or other found disposed in both modes. 



At the foot of the hills which rise to Ben more from 

 Loch na Keal, great beds of trap are seen exposed by the 

 casual sections of water courses, but there are no precipi- 

 tous faces ; while the surface being thickly covered with 

 soil and vegetation, access to the rock is rarely obtained. 

 These beds are horizontal, or but slightly inclined, yet 

 their edges never terminate by stairs like those of the 

 trap before described. In ascending that mountain their 

 regularity varies, and they become inclined as well as 

 curved ; until it is at length impossible to trace either form 

 or position, the whole appearing to be a confused mass 

 shattered in every direction. It is equally impossible 

 to define the place of this transition : it is even uncertain 

 if any defineable boundary exists ; and the same difficulty, 

 it will be remembered, occurs in Sky. 



The composition of this rock is very little varied, and 

 for want of a better general term, that of claystone may 

 be adopted as least exceptionable. 



In general the claystone of Ben more is of a pale blue- 

 ish grey, sometimes varying to a very light tint, com- 

 paratively soft in its texture, and of a mealy aspect. 

 Occasionally it puts on the hardness and sharpness of 

 basalt ; passing through various stages of induration into 

 clinkstone or compact felspar, but retaining its pale blueish 

 colour, and resembling in every respect some of the varieties 

 which occur in Sky and in Arran. In a few situations it is 

 found splitting in a schistose manner. This however 

 is not to be effected by force, but is the result of the 

 action of the weather, the laminae thus detached being 

 sometimes straight, -at others undulated. I observed 

 only two varieties with foreign substances imbedded, the 

 one containing nodules of green earth, the other compact 

 zeolites, apparently solid mesotypes. These latter are 



