MACKIE — TIIE PARALLEL ROADS OE GLEN ROT. 



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fallacy, because the causes which were in operation to form a barrier 

 of alluvial matter could not be at the same time causes of destruc- 

 tion. If any causes were in action capable of forming a barrier 

 of fine earthy deposit to the height of 927 feet above the bottom of 

 Glen Koy, the same causes could not possibly act, at the same time, 

 in producing "a slow waste" in the opposing barrier. Besides, 

 taking the opposite view, that the lake, by the accumulation of its 

 water pent in by the barrier, acquired weight enough to burst it, 

 what has become of the remains of such a gigantic mound? It could 

 not have been washed away totally, and not have left a wreck behind. 

 Macculloch's acute mind saw, too, the difficulty of removing the other 

 earth-barriers, which must have remained after the breaking down of 

 this one; "and other causes," he adds, "which we know not where 

 to seek, must be found to explain the removal of alluvia from points 

 where they appear at present to be, on the contrary, accumulating." 



Such in the main are the natural features presented by Glen Koy • 

 and such the excellent views put forward by Macculloch. That the 

 " parallel roads " have been formed by water action, and are in point 

 of fact ancient lake-shores, few are or have been much inclined 

 to doubt. But the difficulty has been, as we have said, to find the 

 barriers which held up the lake. Macculloch lived before these days 

 of glacial theories, and he looked for a solid barrier of rock or earth ; 

 and it was naturally considered that if such a barrier had existed, 

 some traces of its ruins should remain. Agassiz, some years since, 

 suggested the possibility of the Glen having been blockaded by gla- 

 ciers, but did nothing towards proving the case beyond giving out 

 that suggestion. 



Glacier-action, however, would eliminate all these incongruities 

 from Macculloch's theory. A wall or barrier of ice would melt away 

 and leave comparably to a bank of earth but very little trace indeed ; 

 this is the point Mr. Jamieson has taken up to investigate. Sir 

 Charles Lyell has referred to the parallel roads of Glen Boy, and to 

 Mr. Jamieson's previous labours in that region, in his recent work 

 ' On the Geological Evidences of the Antiquity of Man,' but since 

 the labours there referred to, Mr. Jamieson has communicated a 

 valuable memoir on the subject to the Geological Society of London 

 of such importance that it must attract attention whenever it is pub- 

 lished in the Society's Journal. In it he gives the proofs of ancient 

 ice-action which he has met with in the district, and even assigns the 

 places of the glacier-barrier*; but, if we understand his meaning 



