in the Middle Begion of Scotland. 165 



bottom of these valleys should be grooved and abraded, and 

 the marks of abrasion and grooving should be most conspi- 

 cuous on that side of prominent rocks facing the head of the 

 valley. We shall see how far this conclusion is confirmed 

 by facts. 



I begin with Gareloch, because the markings there are 

 peculiarly distinct ; and I was able to examine them more 

 carefully than those of any other locality. It will be suffi- 

 cient here to give a condensed outline of the two papers I 

 published in 1845. 



Gareloch. — The arrows 8 and 9, in the map (Plate II.), indi- 

 cate the direction of the stride and groovings here. They all 

 point SSE., corresponding very correctly with the axis of the 

 loch. They are very numerous, and while some of them are 

 fine scratches only visible when the surface is wetted, others 

 are grooves several inches, or even feet, in breadth. There 

 is one face of rock 8 feet high and 2 feet broad, in a position 

 not far from vertical, which is entirely covered with groovings, 

 generally about an inch broad, and nearly horizontal. The 

 markings are found several feet under the high-water line, and, 

 though most abundant in low positions, some may be traced 

 at a height of 300 feet above the sea, and three grooves were 

 seen at an elevation of 600 feet, on the top of the ridge which 

 divides Gareloch from Loch Long, and quite conformable in 

 their bearing with those below. The grooves are cut on the 

 edges of the laminae of the mica-slate ; and all those portions 

 of the surface which are not striated are smoothed as if by 

 abrasion. There are many dome-shaped prominent rocks ; 

 and the sides of these which face the head of the valley, are 

 more abraded than those which look in the opposite direc- 

 tion, shewing that the abrading and grooving agent {agent 

 sulcateur of the French geologists) moved from the NNW. 

 to the SSE. Masses of rocks weighing many tons have also 

 been moved in this direction. Stones with striated surfaces 

 are found on the beach ; and on the east side of the valley, 

 at a height of 500 feet, fragments of what seems to be a 

 lateral moraine are visible. In short, marks of tlie ancient 

 existence of a glacier in the valley are numerous and re- 

 markably complete. 



