Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/385

 are said to have drained. This is most remarkably the case in the upper valley of the Spey above Laggan. I have already mentioned the great terrace-mound at the lower extremity of Loch Spey, and nearly on the level of the upper line in Glen Roy. Another very distinct terrace is seen near Garviemore, probably not far from the level of the second line. This terrace much resembles the one at Inverlaire near Loch Treig, but is on a different level. There is another similar flat mound near Glen-Shira Lodge, with a line of washed stones on the hillside, evidently marking a former beach-line.

Still lower down the main valley and in that of the Truim, followed by the Highland Railway, similar indications of the former presence of the sea are very striking. Kingussie, 762 feet above the sea, is about 80 feet under the lowest Glen-Roy Hue ; whilst Dalwhinnie Inn, 1182 feet high, is 40 feet above the highest. In the space between, marks of horizontal lines and terraces are very conspicuous. Thus at the north end of Loch Ericht, a little below Dalwhinnie, and nearly on the level of the upper line, there is a great shingle-deposit of round water-worn stones, showing that the sea has long stood at this elevation. Singularly enough, this old beach forms the watershed between the Spey and Tay in this place. Another very strongly marked terrace is seen for miles on both sides of the Spey near Kingussie. It is about 820 feet above the sea, and thus rather lower than the third Glen-Roy line (about 30 feet). This difference of level is very small, considering that Kingussie is 30 miles from Glen Roy in a direct line, and 15 from Loch Laggan, where the lowest line terminates in the Spean valley. The breadth of this terrace, the flatness of the surface, broken from place to place by deep irregular hollows with pools of water at the bottom, and the distinct cliff where it meets the slope of the hill, prove that the sea has stood here for a long time. At Loch Gynac, a small lake in the valley behind Kingussie, there are three terraces quite similar to those in Glen Roy, but far inferior in extent. Two of them also, according to some aneroid observations I made, are nearly on the level of the second and third, or upper terraces in Glen Roy. There are other similar indications of the presence of the sea in this vicinity ; but I shall only refer to some distinct traces of horizontal lines on the declivity of the hill forming the south side of the Laggan valley on the Spey. In regard to all these lines and terraces in this district, they appeared to me to show that the water had retired, or the land risen, by sudden starts, as it were, not by a slow, regular, and continuous process. In this they agree with the phenomena of Glen Roy, and thus confirm the view now given of the origin of its lines.

The exact coincidence of the hues with certain cols or passes between the valleys has to many appeared an almost insuperable difficulty in the way of the theory of their marine origin. It has been felt as a strong objection to this marine theory, that the sea in its descent should pause three or four times, just at the level of these three or four openings in the hills. It may lessen this difficulty if we consider that the currents from the west.