by Professor Studer. 171 



studies respecting another and entirely different part of our 

 science, by the numerous traces of alterations of the surface, 

 which have occun^ed during the most recent geological times. 

 The extraordinarily broken lines of coast — the cutting off, at 

 the sea coasts, of the formations which extend obliquely 

 across the island — the isolated occurrence at the shores of 

 limited masses of formations which, in other places, are 

 widely extended, all indicate great changes of level, to which 

 testimony is also borne by terraces, in some instances re- 

 markably well preserved, occurring both on the coasts and 

 in the interior. The great thickness and extension of the 

 Till^ together with the occurrence of erratic mounds of earth 

 and heaps of stones in all the valleys, point to currents, for 

 the origin of which, unless they were currents of the sea, 

 space would appear to be wanting. In many places, finally, 

 polished and rounded, or furrowed and scratched rocks, have 

 been observed of the same kind as those which occur among 

 the Alps and in their neighbourhood; and from them the 

 former occurrence of glaciers in this country has been in- 

 ferred. Many questions relating to these phenomena are, as 

 yet, involved in doubt ; and it would be presumptuous for me 

 to attempt to decide in regard to matters which, by native 

 geologists, after niuch careful investigation, have been left 

 undetermined. To the assumption of former glaciers, I feel 

 quite favourably disposed ; although it appears difficult to 

 believe in so unlimited an extension of them as must be 

 assumed in this case, as well as in many others, if we attri- 

 bute the whole phenomena of erratics to this agency. Many 

 of the higher hills exhibit, in various places on their flanks, 

 that peculiar elevated background, widened out into a caul- 

 dron shape, which in the Alps serves as the chief source of the 

 glaciers. Instances of this kind are met with in Glen Nevis, 

 in Glencoe, on Goatfell in Arran, and in Capel Cerig in 

 Wales. In Glencoe, also, Forbes directed my attention to 

 smoothed rock surfaces, and rounded prominences of the black 

 porphyry, which was formerly mentioned, and was stated to be 

 split into plates. These were undistinguishable from similar 

 phenomena in the neighbourhood of our glaciers. On the west 

 side of Salisbury Crags at Edinburgh, two smoothed rock-sur- 



