Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/331

 which these two lie. It is here necessary to say that the two lines on the right now described are parallel to each other, and correspond precisely in level with the fragments of the two upper ones visible on the opposite side.

As we proceed down the glen a river is seen entering at the left hand equal in size to the Roy, and falling into it by a cascade which rushes over a rocky bed. Here a great series of terraces is found, forming a large terreplein at the top of this glen which I have called lower Glen Roy. These terraces are of different levels, as may be seen both in the section and in the views that accompany this paper. The highest of them will hereafter be proved to lie on a level with a third line, to be described in the course of this investigation. It falls off however by many successive stages of terraces, and numerous smaller ones are also to be seen descending down to the very bed of the river, skirting its banks and accompanying its course. The bottom of the glen is here an alluvial flat, as the above mentioned section will show. Between the two upper lines on the right hand an intermediate one now becomes visible for a space of about half a mile: I did not measure it, but to the eye it appears equidistant from both. At this point the two lines now described suddenly quit the rocky face described on the right hand, and continue their courses along the alluvial slopes of the declivities which follow; where also they acquire their greatest breadth and distinctness.

I forbear giving the breadths in all the places where I measured them, because it is not important. The profiles will show the principal varieties. In detailing their measures I must remark that it would be impossible to describe the precise geographical point measured, and such often is the curvature at the entering and salient