Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/327



Before examining any of the theories which have been proposed to explain the singular appearance which this glen exhibits, I have judged it expedient to describe with as much accuracy as possible the appearances themselves, without entering on the question of causes, or prejudging in any degree the case. In thus describing it, I have preferred beginning at the source of the river, or rather at the commencement of the valley, since the rivers which form the Roy arise as mountain torrents, forming a junction in the middle of a valley of considerable magnitude.

A low hill of granite skirts the boundary between the source of the Spey and the valley of the Roy. At the foot of this hill, in a slightly elevated boggy plain, is found Loch Spey, which by a declivity for some time scarcely perceptible runs eastward through Badenoch to fall into the Moray firth. The western end of the boggy plain just mentioned stretches for a few hundred yards beyond the head of Loch Spey, and then descends by a sudden step into the upper valley of Glen Roy. This valley is of an oval form,