128 THE STETJCTTJEE OF THE [vol. Ixxvili, 



DiSCUSSlOJf. 



Mr. Gr. Barrow regretted that he had been unable to follow the 

 Author in his repeated references to different districts. Having 

 visited much of the area, he did not agree either with the Author's 

 view of the structure of the country or his nomenclature of the 

 rocks. The existence of the ' nappes ' shown on the map seemed 

 most unlikely, as the speaker felt sure that individual beds could 

 be traced across from one to the other. Judging from some of the 

 lantern-slides exhibited, he suspected that the supposed ' nappes ' 

 were simply different aureoles of thermal alteration, similar to 

 those mapped out in the South-Eastern Highlands, which were 

 shown in detail in the pamphlet prepared by the speaker for the 

 use of the Greologists' Association, at the Dundee Meeting of the 

 British Association. 



Dr. J. S. Flett said that everyone interested in Highland 

 geology admired the enthusiasm with which the Author had 

 attacked the problems under discussion. It was a task of extreme 

 difficulty to unravel the structure of the Southern Highlands, and 

 no means of accomplishing that end could be neglected. Among 

 others, recent geological work in the Alps has furnished new ideas, 

 especially in regard to the features of ' nappes,' which were sure 

 to be applied to the Scottish Highlands, and were likely to prove 

 of cardinal importance. In his paper the Author had suggested 

 that in Argyllshire three ' nappes ' could be recognized. He had 

 discarded the sequence hitherto adopted by Scottish geologists, 

 and advanced a new correlation which was in harmony with his 

 views of the structure. 



The speaker, while recognizing the attractive character of the 

 Author's hypotheses, did not feel convinced that the solution now 

 offered was established on an incontrovertible basis. The vast 

 movements postulated did not seem to have produced a corre- 

 sponding effect on the outcrops. The rocks of Ballachulish and 

 Loch Awe were very much those which would be expected to occur 

 there if no ' slides ' existed, or if the ' slides ' were of small 

 magnitude. The Ballachulish slide, for example, did not seem, in 

 a large part of its course, to have shifted the outcrops to a notable 

 extent. This might be because, as the Author suggested, the 

 movement was very nearly parallel to the bedding-planes. But 

 great movements could not be so confined, and we might expect, 

 occasionall}'- at any rate, to find that beds were brought into juxta- 

 position which normally were widel}^ separated. So far as the 

 speaker had seen, the evidence both of the maps and of the natural 

 exposures was not in favour of the large movements in which the 

 Author believed. It was very desirable that a clear case of 

 transport, with difference of facies in the exotic and the auto- 

 chthonous beds and something resembling a visible thrust-plane 

 should be brought to light. The Author's slides Avere practically 

 confined to the outcrops of the Central Highland Series (from the 



