1873.] ARGYLL — LAKE-BASINS IN ARGYLLSHIRE. 509 



hibiting the escarpment and the other the slope side of strata, dip- 

 ping more or less steeply to the N.W. Loch Awe occupies a differ- 

 ent position ; it lies in a synclinal trough. The slates constituting 

 the base of Ben Cruachan dip steeply into the bed of the lake 

 on the northern side ; and the dip of the rocks into the same basin 

 is almost equally steep on the southern side. The islands in the 

 middle of the lake exhibit vertical strata. The lake finds its exit 

 through a gap at the foot of Ben Cruachan — a gap which marks a 

 great structural break or displacement. The eastern side of this 

 gap is formed by the steep sides of Ben Cruachan, rising to a 

 summit 3600 feet above the sea ; whilst the western side is formed 

 by the broken escarpment of beds dipping at a wholly different 

 angle, and forming the boundary of a large tract of country of much 

 lower elevation than the mountainous district which terminates in 

 Ben Cruachan. The bed of Loch Awe, therefore, lies in a hollow or 

 basin which is sufficiently accounted for by structural causes ; and 

 where these exist so obvious and so sufficient, it would be unrea- 

 sonable to account for that basin by the denuding agency of ice. 

 Where great subsidences of strata have undoubtedly taken place, it 

 is not reasonable to suppose that such movements would stop at 

 a particular level ; and every depression deeper than others would 

 naturally become a lake-basin. 



Between Loch Eyne and Loch Awe a series of hilly ridges are 

 composed of slates with associated granites, which seem to have 

 burst along the lines of bedding when the slates fell in, those lines 

 being the lines of least resistance. These hills are full of small lake- 

 basins ; and these are generally of a character which seemed to the 

 author to be incompatible with the theory that they were exca- 

 vated by glaciers, or by ice in any form. He mentioned three, of 

 which the first was Loch Leckan. This lake is about a mile long ; 

 it lies in a hollow between two granitic ridges, which, however, are 

 of small elevation. At one point this little lake is 18 fathoms 

 deep. Although the upper part of the basin is in granite, the 

 lower part of it is probably in the slates, since a quartzite bed 

 appears on the shore at the upper end. There are no marks of 

 glaciation on these beds, though of a character well fitted to retain 

 them. There is no hill near which could form the gathering-ground 

 of a glacier capable of doing such excavating work; and the 

 difficulty of attributing this basin to ice-action is increased by the 

 position of the second of these small lake-basins, namely Loch-na- 

 Craig. This lake is separated from Loch Leckan only by a very 

 narrow ridge : it is 9 fathoms deep, of a circular form ; and its 

 level is about 150 feet above Loch Leckan. If this lake-basin 

 had been due to any powerful abrading agent capable of digging 

 such a hole in granite, it is impossible to conceive how such agent 

 could have left the narrow dividing ridge standing, which separates 

 it from the lower basin of Loch Leckan. There is nothing to in- 

 dicate that this deep little hole lay in the route of any conceivable 

 glacier ; and its position and character are, if possible, still less 

 capable of being reconciled with the action of a general ice-sheet. 



VOL. XXIX. — rARX i. 2 m 



