98 ON THE CONVOLUTIONS OF STRATA, 



When we undertake to account for the convolutions of the 

 killas, by the forcible invasion of granite, one material point is 

 to show, contrary to the opinion entertained as yet, I believe, 

 by all geologists but those of the Huttonian school, that gra- 

 nite has been the latest formed of the two. The scenes in 

 Galloway, where these substances meet, prove this, I conceive, 

 beyond dispute; but they prove it over much in one point of 

 view, since they show the arrival of the granite at its present 

 place, to have been posterior, not only to the formation of the 

 strata of killas, but also to their convolutions when in a state 

 of softness, and to their subsequent consolidation. It must, 

 therefore, be admitted, that this mechanical etfect cannot have 

 been produced by the particular granite there exhibited ; but 

 the circumstances which the junction presents to view, autho- 

 rise us to believe, that another granitic mass, acting in a for- 

 mer period, with the same powers, but when the killas was in 

 a soft state, has been the agent of these convolutions. It be- 

 comes, therefore, of great importance in this inquiry, to make 

 a clear statement of the mode in which the introduction of the 

 granite into its present place has been effected in this authen- 

 tic instance. 



In that view, I shall ask permission to lay before the Socie- 

 ty, the details of some observations, which, in general terms, I 

 mentioned in a former communication. 



In the year 1790, I read an account in this Society of my 

 observations on one of those granitic masses which reaches 

 from Loch Ken to the valley of Palnure, a short abstract of 

 which has been published in the History of the Society at 

 that period. It is there stated, that I had traced the junction 

 of this mass with the neighbouring rock, in a complete circuit 

 of it, which I made in company with the Honourable Thomas 



Douglas 



