on the Mountain Cruachan. 13*7 



by the intrusion of some other rock. The uniformity of their 

 dip seems a sufficient reason to reject the former explanation, and 

 their present appearance is more probably derived from both the last 

 mentioned causes acting on different points. Concerning the action 

 of water or other similar causes we can only conjecture, but of the 

 latter we have occasional proof in the actual existence of masses of 

 trap rock overwhelming them in some places, and doubtless Con- 

 cealing them entirely in others. It may perhaps be owing to this 

 rock and to its subsequent destruction only, that their present state 

 is to be referred. I shall therefore conclude these illustrative re- 

 marks by a few words respecting the trap rocks which occur in the 

 vicinity of Cruachan, and which are in many places so intimately 

 connected with these detached portions of the secondary strata. 



The nearest mass of these substances is a long mountain ridge 

 which occupies part of the northern shore of Loch Etive, descend- 

 ing towards the western sea and skirting the plain of Connel. 

 It is in this place well known to all who have travelled the west 

 Highlands, since the road passes under large rocks of the conglo- 

 merate which is connected with it. It is equally familiar to 

 those who visit Oban, since the surrounding country and the 

 neighbouring islands are covered with more or less extensive 

 masses of it, in some cases reposing on the older schists, which 

 form the visible basis of this country, in others upon the sand- 

 stone strata already described. It is in this latter case that it pro- 

 duces the effect already alluded to of partially concealing the 

 masses of sandstone, so as to give an appearance of separation 

 where no real one exists. In some cases it is also probable that 

 it has actually dislocated and separated them, intruding among 

 them as all the rocks of this family do, from below. Hence it 

 assists us in explaining the state of the sandstone formerly described, 



