Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/341

 becomes again visible on hills below it of a slope precisely similar. It must at present therefore be regarded as one of the numerous difficulties attending this very difficult subject.

The upper line becomes also invisible on the right opposite to this place, and shortly after, the whole disappear on this side, though no material alteration takes place in the form or structure of the hills. About a mile before we arrive at the junction of the Roy and Spean, the valley expands, and here the lowermost line again makes its appearance, continuing its course round Meal Derig to the side of Glen Spean, where it disappears. The same line shortly after reappears on the right side, and from hence it can be traced with more or less difficulty as far as Teindrish, over a various surface of very slight inclination, until it finally vanishes. At Keppoch the Roy falls into the Spean issuing from Loch Laggan, and here it loses its name; while the Spean holds its course westward for a space of five or six miles till it falls into the Lochy.

On the left bank of the Spean, near the junction of the Roy, a line is visible which is found by the spirit level to correspond with the lowermost line of Glen Roy. It runs about three or four miles up the valley over a surface of moderate inclination, yet although the curvature and structure of the opposite hills which bound the Spean are similar, it is not found on the right bank. It continues to hold its course westward with more or less obscurity, from the junction of the Roy and Spean along the declivities of the high mountains Ben na 'chlianach, Scuir rinish, and Carn derig, which bound this wide valley to the south, finally disappearing opposite to Teindrish, and nearly in the same meridional direction. The valley is here of such dimensions that the opposite lines are about four miles asunder. Its bottom is extremely irregular, offering rather an accumulation of low hills than a valley properly so called. But in