Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/343

 This is among the best marked of those which are any where to be found, its breadth being not less than 70 feet and its inclination among the least of those which I measured. It is important to notice that the opposite sides of Glen Turit are very little dissimilar either in shape or composition, although they do not exhibit equal traces of the lines; and it is still more essential to remark that the bottom of this glen is of solid rock and not of alluvial formation; since in the course of the examination it will be important to remember that the operation of ordinary causes is to diminish, not to augment its elevation.

Where this solitary line disappears in consequence of the rise of the glen, a level space occurs without a stream, but in no long time it produces one, which running westward forms the water of Gloy and enters Loch Lochy beyond Lowbridge.

When I said that the upper line which is prolonged so far into this glen is stopped by the rising of its bottom, I did not intend to speak precisely: it ceases in fact for some space before, but evidently from the sliding of the face of the hill into the stream. That which it is important to note is, that if it had been prolonged it would have met the bottom of the glen, which may be considered as there forming an intermediate hill between Glen Gloy and Glen Roy, and thus interrupting the continuous level which should take place between them at the height of the upper line, It is this part of the fact alone which is important, and important in more views than one, as will appear when I shall attempt to investigate the cause of these lines. I may remark that these altitudes are not estimated, but were observed by the spirit level.

I have reason to regret that a tempestuous season prevented me from examining Glen Gloy with the same care which I had bestowed on Glen Roy. The requisite observations, attended with