316 Geological Society : — 



along different lines of elevation. Taking this new deposit to be 

 the Old Red Sandstone, the author asks how it was removed, and 

 points out difficulties in the way of supposing the removal to have 

 been either by submergence or by subaerial agencies. 



His Grace then stated that Mr. Geikie admits that the agencies 

 of erosion have been guided in their work by the prevailing strike 

 of the strata, which strike is followed along the same line by the 

 larger faults, and by the anticlinal and synclinal axes, — at least as 

 regards the general trend. He then pointed out that in reality all 

 the great physical features of Scotland take the same N.E. and 

 S.W. direction. He therefore considered that Mr. Geikie had 

 understated the case of the coincidence of certain physical fea- 

 tures, and had entirely omitted all mention of others, such as the 

 appearances of subsidence and dislocation to be observed in the 

 Western Islands, and the relations existing between dislocated sedi- 

 mentary strata and apparently intrusive rocks. 



In supporting his argument by special facts the Duke of Argyll 

 endeavoured to show that the whole valley-system of Argyllshire 

 may be accounted for either by faults, foldings, subsidences, or anti- 

 clinals, mentioning in particular that Loch Tyne occupies the bed 

 of an enormous fault, that Loch Awe lies along the line of a great 

 subsidence of the metamorphic slates, and that the gorge of the 

 Brander Pass lies along the line of a great fracture connected with 

 the subterranean movements which brought up the granites of Ben 

 Cruachan, with many other instances of a like nature, in discussing 

 which he especially demurred to Mr. Geikie' s theory that the trans- 

 verse valleys and gorges have been formed by two streams, each 

 working backwards towards its own source, until the ridge which 

 divided them was finally destroyed. 



His Grace also remarked that the mineral condition of the 

 granites at the time of the subterranean movements was such as 

 would facilitate the transmission of earthquake-waves, and the 

 condition of the slates was such as necessitated fracture when 

 those waves were propagated beneath them. 



In conclusion the author contested Mr. Geikie's statement of the 

 symmetry of river- valleys and uniformity of mountain-heights, and 

 contrasted the philosophy of the older geologists with that of the 

 advocates of subaerial denudation. 



February 26th, 1868. — Prof. T. H. Huxley, LL.D., F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. " Notes on the formation of the Parallel Roads of Glen Roy." 

 By C. Babbage, Esq., F.R.S. 



Accepting the theory that these roads were formed on the margin 

 of a lake, the author discussed the mode in which this formation 

 took place, objecting to the view of its having occurred through the 

 piling up of pebbles by wave-action, or the accumulation of blocks 

 by rain washing them down the hill-side. 



Mr. Babbage expressed his opinion that the material of which 



