1851.] HOPKINS-— ERRATIC BLOCKS OF THE S. HIGHLANDS. 23 



miles southward, and probably to its southern extremity, for there 

 can be little doubt of this having been one of the courses by which 

 the blocks of the Clyde have reached their present locality. The 

 other obvious course is that afforded by Loch Long. 



Besides the valleys above-described, there is one, two or three miles 

 long, which runs directly from the head of Loch Long to the village 

 of Tarbet on Loch Lomond. Numerous blocks are found along this 

 valley, through which similar blocks have manifestly been transported 

 from one loch to the other, probably from Loch Long to Loch Lo- 

 mond, since that direction of transport appears more consistent than 

 the opposite one with the general direction of dispersion in that 

 quarter. There is also another valley, running directly north, from 

 the northern extremity of Loch Lomond to Tyndrum, which might 

 have afforded an access for blocks to that end of the lake ; but on 

 examining this valley for some distance, I was unable to find in it a 

 single block of granite. 



There is also another course along which blocks of grey granite 

 have found their way to the upper part of Loch Long. The valley 

 of Glencroe, along which runs the road from Tarbet to Inverary, lies 

 immediately to the south of the Cobler, a mountain mentioned above. 

 In proceeding westward along this valley from the lake, we observe 

 blocks of grey granite, but neither large nor numerous until we ap- 

 proach a small, but rapid stream descending into Glencroe from the 

 central group of mountains about Ben Nime, where a large mass of 

 grey granite, as already described, is found in situ. The gully, down 

 which the stream descends, is filled with blocks of grey granite, many 

 of these being of considerable magnitude. The smaller ones only 

 appear to have been carried forward along the valley of Glencroe. 

 Proceeding westward along the road from this point the blocks 

 entirely disappear, until we descend towards the head of Loch Fyne. 

 Round the head of the loch they are very numerous, but instead of 

 being of a dark-grey colour, they belong to the whiter kind of granite 

 with large crystals of felspar. They are very numerous along Glen 

 Fyne, which extends directly northward from the head of the loch, 

 and have manifestly proceeded from a great mass of granite about 

 four or five miles north of the loch. This granite extends across 

 Glen F}me to the west, and on the east it extends to the north of 

 Loch Sloy, forming the source from whence the blocks of whiter gra- 

 nite, which have descended from that lake to Loch Lomond, have un- 

 doubtedly been derived. 



The greater portion of the blocks on the shores of Loch Fyne have 

 evidently come down Glen Fyne, but a portion, although probably a 

 small one, has descended the valley along the lower part of which 

 the road before-mentioned passes from Loch Long to Inverary. This 

 valley runs up nearly in the direction of Loch Sloy, and penetrates, 

 I have no doubt, into the mass of granite just mentioned. Its lower 

 termination is at Ardkinglas, one or two miles from the head of the 

 loch. 



In this part of the Highlands there is art important group of 



