256 PROCEEDINGrS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



tions have had comparatively very little to do with the origin of the 

 hills and valleys of the Highlands. Their form is mainly due to 

 atmospheric powers of waste acting slowly and gradually through 

 uncounted " millions of years." The mountains have been carved 

 out of the original thickness of the strata of which they are com- 

 posed. The valleys are nothing but the hollows out of which vast 

 masses of material have been removed ; and, farther, this removal 

 has not been effected by convulsions of any kind, but merely by the 

 streams which now occupy the bottom of the glens, and, during the 

 Glacial period, by continuous masses of ice which passed downwards 

 from a few central ridges to the sea. This theory is stated and re- 

 stated in many forms, with some variety as to the amount of allow- 

 ance made for subterranean movements, but always with a careful 

 limitation of that allowance to just so much of it as will help the 

 favourite theory, and will not embarrass it. I quote one of these 

 forms of statement that we may have the theory before us in the 

 author's words, " The conclusion, therefore, to which an attentive 

 examination of the present surface of the country points, is that 

 although the rocks have unquestionably suffered much from subter- 

 ranean commotions, it is not to that cause that the present external 

 forms are chiefly to be traced ; that the mountains exist, not because 

 they have been upreared as such above the valleys, but because their 

 flanks having been deeply cut away, they have been left standing 

 out in relief; and that the valleys are there not by virtue of old 

 rents and subsidences, but because moving water, with its help- 

 mates frost and ice, has carved them out of the solid rock." 



jS'ow, as regards at least that large area of the West Highlands 

 which is included in the county of Argyll and its adjacent islands, 

 my belief is precisely the reverse of the theory here stated — that 

 although the atmospheric agencies of waste have produced great 

 modifications of the surface, the form of the hills and valleys has in 

 the main been determined by the action of subterranean forces, that 

 the mountains have not been cut or carved out of the tliickness of 

 some ancient tableland, but have mainly arisen from upheavals and 

 subsidences, and lateral pressures, which have folded them and 

 broken them into their present shapes — that the work done by 

 rivers in excavating their own course has been comparatively small, 

 that they have not cut out for themselves the valleys in which they 

 flow, but have taken channels determined for them by movements 

 from beneath. 



In conducting this argument, then, let us look in the first place for 

 such facts as are admitted on both sides, and, if there be any, for such 

 principles applicable to those facts as are not capable of dispute. In 

 this case it is satisfactory to find that both in respect to fact and to 

 principle there is at least some common ground to start from. 



First, there is the fact that the mountains of the Highlands are 

 composed for the most part of strata which are not horizontal, but 

 inclined at every variety of angle. This cannot be stated in language 

 more expressive than that employed by Mr. Geikie himself. He says 

 " The strata of sand and mud, accumulated to a depth of thousands of 



