264 



PKOCEEDIN&S OF TSll GEOLOGICAL SOCIETY. 



[Feb. 5, 



rain, falling on rocks already hardened and contorted, is compared 

 with the action of water draining out of a material perfectly loose, 

 saturated with moisture, and destitute of any guiding structure. 

 Por my own part I think this illustration enough of itself to upset 

 the theory. I should say that the mechanical process which makes 

 little rivers in wet sand from water welling out of its very sub- 

 stance, or coming with gTcater force from higher elevations, cannot 

 possibly be the same which, under any conceivable conditions, cut 

 the valleys of the Highlands out of the hard crystalline rocks of 

 which the mountains are composed. 



I pass, however, from these general considerations, which are 

 useful only as showing the antecedent improbabihties involved in the 

 extreme theories of erosion. I proceed now to test them on the field 

 of fact; and 1 take, in the first place, that district of Argyllshire which 

 lies between the northern banks of Loch Awe and the Frith of Clyde. 



This is a district from which Mr. Geikie takes several of his 

 illustrations. It is one with which I am well acquainted in detail ; 

 and it is one including within itself a grand display of all the 

 characteristic phenomena for which it is necessary to account. I 

 venture to assert, in opposition to Mr. Geikie, that almost the whole 

 valley-system of this district, including both the longitudinal and 

 the transverse valleys, is best accounted for by faults, by foldings, 

 by subsidences, and by anticlinals among the strata. 



To begin with — Loch Pyne itself, which is one of the main fea- 

 tures of the country, and is well known to be one of the most promi- 

 nent examples of that longitudinal valley-system which is so marked 

 upon the map of Scotland, occupies, as I believe, the bed of an 



Fig. 1. — Section across the bed of Loch Awe. 



Glen Strae. . Kalbnm Castle. G-len Orehy. 



Ben Cruachan. — '==^ 



Loch Awe. 



A. Slates on the opposite sides of Loch Awe. 



B. Vertical slates on the Island of Freuchlin. 



immense fault. Loch Awe, another of the valleys which assume the 

 same general direction, lies along the line of a great subsidence or 

 falling inwards of the metamorphic slates, and occupies the bed of 



