366 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



nation in the disturbed strata. In the mica-slates of a large part of 

 Argyllshire we have regular anticlinal dips, ranging with remarkable 

 equality and uniformity along considerable lines of country ; we have 

 no intrusive rocks where a section is afforded of an anticlinal ridge to 

 the depth of some 1500 feet ; and where we do meet with the intru- 

 sive rocks, we find them not causing, but themselves conforming to 

 the dip. 



I do not apprehend that he who makes such a suggestion can be 

 legitimately called upon to go farther and account for the falling in- 

 wards of the mica-slates. 



It is not the object of this paper to connect the local phsenomena 

 to which it refers with any general theory as to the origin of moun- 

 tainous irregularities on the surface of the earth. The universal ap- 

 plicability of any one of these theories seems hardly consistent with 

 the evidences of variety which mountainous districts present, as regards 

 almost all the circumstances of their first and successive elevations. 

 But, though there are many conceivable conditions under which the 

 action of gravity might have produced such a falling in of the strati- 

 fied crust from the withdrawal of internal support, it is impossible 

 not to be struck by the explanation which the " shrinkage " theory 

 of M. Elie de Beaumont and others would afford of the whole struc- 

 ture of this part of Scotland. The mineral character of the mica- 

 slates has been long recognised as in all probability due to the meta- 

 morphic action of heat ; and I have already shown that there are 

 evidences of this mineral character having been fully acquired before 

 the eruption of the granites. That it is not due to that eruption is 

 farther evident from the fact of its prevalence and uniformity where 

 no such rocks appear at all. It is not, therefore, an improbable sup- 

 position, considering the evidence which these rocks afford us, that 

 they had been exposed to a very high temperature from some great 

 general cause, widely operative over the surface of the planet ; and if 

 that heat were a decreasing one, shrinkage or contraction of the sub- 

 terranean masses would inevitably result ; which again would be fol- 

 lowed by collapses inwards of the outer crust. At the time when 

 these collapses apparently took place in the county of Argyll, the 

 subterranean heat was still so near and so great, that the falling in of 

 the strata to the depth of some 1500 or 2000 feet was sufficient, as 

 we have seen, to force up along their surfaces great masses of granite, 

 so little cooled as to be in a viscous, if not in an actually liquid 

 state. 



It would be a matter of much interest, if the crystalline rocks of 

 the Highlands, which seem to belong to an age primseval even as 

 regards the long seras of geology, should be found thus pointing to 

 pheenomena of a primaeval character. 



