Glaciers in Scotland in Ancient Times. 35 



hills on the east side of Gareloch had dressed surfaces to the 

 height of more than 1000 feet. I found no distinct striae, 

 however, at a greater elevation than 310 feet ; and while ad- 

 mitting that the action of a glacier might extend to this 

 height, or somewhat beyond it, I was disposed to attribute 

 the abrasion of the tops of the ridges and all the higher por- 

 tions of the declivities to icebergs. On this occasion, how- 

 ever, I found strise on the top of the ridge dm (Figs. 5 and 6), 

 right west from the farm of Little Rahaen, and at 600 feet of 

 elevation. There is an area of beautifully dressed rock here, 

 about a quarter of a mile in breadth, nearly level, and thinly 

 covered with peaty turf {d in fig. 5, and in the section below 

 it). The covering has been washed off at many points, and 

 the rock is seen as smooth as a hearthstone. At one spot I 

 found a distinct groove half an inch broad, 3 feet long, and 

 quite straight. The bearing was N. 30 W., which is very 

 correctly that of the ridge, and of Gareloch valley. There 

 were two others beside it, but fainter and shorter. The value 

 of the groovings is, that they indicate the precise direction in 

 which the abrading agent moved, and the indication in this 

 case is important. Groovings in a deep and narrow valley 

 like Gareloch, whether cut by a glacier, an iceberg, or a cur- 

 rent — supposing a current capable of doing it — might be ex- 

 pected to have a general correspondence with the axis of the 

 valley, because its steep sides would compel the agent to 

 move in a determinate direction. But here the groovings oc- 

 cur on the very summit of the ridge, where the agent was 

 free to move in any direction, and they indicate a motion in 

 the very line which stony masses driven along by a current 

 would most certainly have avoided — a motion right along the 

 crest of a ridge, with a steep declivity on each side, towards 

 which heavy bodies would inevitably have tended. It is con- 

 ceivable, however, that a very large iceberg, moving steadily 

 in a determinate direction, either in consequence of the im- 

 mensity of its mass, or from being pressed on each side by 

 fixed or floating ice, might groove the rock in this way. But 

 I think there is a simpler and more satisfactory solution of the 

 problem. Rocks striated horizontally are found in the Al- 

 pine valleys, 1500 feet above their bottom, — {Forbes Travels 



