During the formation of the upper terrace, the waters escaped through the westernmost tributary of the River Spey, in the direction of the northeast corner of the wood-cut, and during that of the lowest terrace, at the eastern end of Loch Laggan, also through the valley of the Spey. The state of preservation of the parallel roads is such as to prove that no disturbance of any importance can have taken place in the country since they were formed. Far from believing, therefore, that these remarkable shelves are ancient sea-beaches, I am prepared to maintain, that, had the area occupied by them been submerged only for a few days, under an ocean rising and falling for several feet with every tide, no vestige would have been left of their former existence. [C] The wood-cut on p. 730 is a reproduction of the little map accompanying a paper of mine upon "The Glacial Theory and its Recent Progress," printed in the "Edinburgh New Philosophical Journal" for October, 1842. I might have greatly improved the topography, and represented more accurately the details of the phenomenon, by availing myself of the much larger and very minute map recently published by Professor Thomas F. Jamieson, of Aberdeen; but I thought it advisable to leave my first sketch as I presented it twenty-two years ago, in order to show that Sir Charles Lyell is mistaken in ascribing (see "Antiquity of Man," pp. 260, 261) the discovery of the glacier of Loch Treig to Professor Jamieson. A comparison of his statements with mine will show that the solution of the problem offered by him is identical with that proposed by me, as he himself candidly admits ("Quarterly Journal of the Geological Society" for August, 1863, p. 239). I have only one fault to find with his observations, and, as I have never revisited the locality since, this remark may satisfy him that my examination of its features was not so hurried as he supposes. Professor Jamieson confounds the effects of two distinct glaciers moving in different valleys as the action of one and the same glacier. In my paper, it is true, I made no allusion to the great glacier of Glen Spean, the existence of which I had recognized along the river from Loch Laggan nearly to the Caledonian Canal. I publish my observations upon this great central glacier for the first time in the present article, having omitted them in my contributions upon this subject to the scientific periodicals of the day simply because I thought best not to complicate my exposition of the facts concerning the parallel roads by considerations foreign to their origin, convinced as I was, from the manner in which the glacial theory was then received, that they would not be understood, and still less admitted. But now that all the geologists of Great Britain seem to have given their adhesion to it, I may be permitted to state that I already knew then, what Professor Jamieson has overlooked in his latest paper,