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Proceedings of the Royal Society 
He referred to the ample means of cutting through and remov- 
ing detrital matter possessed by streams and rivers, mentioning 
particularly the enormous cliffs of detritus cut through by the 
Rivers Spean and Spey. 
He next proceeded to discuss the theories of other geologists. 
With regard to the theory that the parallel roads were formed 
by the sea, he adduced arguments to show, that this view was im- 
possible, inasmuch as the “roads” should in that case have all 
stood at the same level ; whereas, in the different glens, they stood 
at different levels. Moreover, it had been found, that old river 
courses existed, by which the water in G-len Gfluoy flowed into the 
water in Glen Roy, and that the water in Glen Roy flowed through 
Glen Glaster into Loch Laggan, — a state of things utterly fatal to 
the marine theory. 
With regard to the blockage of the lakes having been formed 
ice , the following objections were stated : — 
ls£, The improbability that some of the glens were filled with 
water, whilst others were filled with ice, the temperature of those 
glens being all much the same, in consequence of nearly equal 
altitudes above the sea. 
2d, The impossibility of getting a glacier to come to the exact 
spot, where the lakes stopped, to form barriers several miles long, 
so solid and permanent in structure, as to prevent the escape of 
the water from lakes above 300 feet deep. 
The author concluded by referring to the numerous examples in 
the Lochaber district, of boulders perched on tops of hills, and of 
rocks smoothed and striated. These phenomena had been ascribed 
by some geologists to the action of land-ice. But, coupling with 
these high-perched boulders, the occurrence of kaims or eskars on 
the sides of the hills (above the parallel roads), and therefore 
formed before the Lake period, the author was inclined to ascribe 
these phenomena to one agent — viz., a sea loaded with ice, when 
the land was submerged, and to a strong current in the sea, from 
the north-west, which swept over the submerged land, and through 
such valleys as Glen Spean and Glen Roy. The lakes, he referred 
to the period when the land was rising out of the sea. Their 
beaches were formed on the marine detritus; — which also for a time 
dammed back the lake waters. 
