68 STUDIES, SCIENTIFIC AND SOCIAL chap. 



rock just described have been exposed to the action of the 

 atmosphere, perhaps since the ice left them, and have thus 

 become more or less roughened or even disintegrated ; but 

 where the rocks have been protected by a covering of 

 drift, or even of turf, and have been recently exposed, they 

 often exhibit numerous parallel striae, varying from the 

 finest scratches to deep furrows a foot or more in diameter. 

 Fine examples are to be seen near the lakes of Llanberis, 

 and they occur more or less frequently in every glaciated 

 country. The accompanying illustration (Fig. 12), which 

 I owe to the kindness of Mr. Godfrey Bingley, of Leeds, 

 shows a striated surface of Shap granite at Wasdale Crag, 

 Westmoreland. Perhaps none of the effects of ice so 

 clearly demonstrate the action of glaciers as opposed to 

 that of icebergs, owing to the general constancy of the 

 direction of the striae, and the long distances they may 

 be traced up and down slopes, with a steadiness of motion 

 and evenness of cutting power which no floating mass 

 could possibly exert. Sir A. Geikie tells us that in Gare- 

 loch, Bute, and Cantyre the striations on the rocks run 

 up and over the ridges, and are as clearly shown on the 

 hill-tops as in the valleys. Mr. D. Mackintosh states (in 

 his paper on the " Ice-sheet of the Lake District and of 

 North Wales ") that in the valley above Windermere the 

 striae cross Rydal Fell, Loughrigg Fell, and Orrest Head, 

 ascending and descending their slopes, often obliquely. 

 But it is in the United States that the most remarkable 

 rock-groovings are to be found, extending over a large 

 portion of the North-eastern States. In his report on 

 " The Rock-scorings of the Great Ice Invasions," Mr. T. C. 

 Chamberlin gives many fine illustrations, from photo- 

 graphs, showing striae and grooves along sloping, curved, 

 or vertical surfaces, the striae following the changes of 

 curve, so that the grinding material must have been slowly 

 forced into close contact with the irregular surface. Of 

 one of these examples Mr. Chamberlin says : — 



' ' The climax of adaptability is reached in the striation of warped 

 and twisted surfaces, and of tortuous valleys. One of the most 

 remarkable known instances of this within the limits of photographic 

 illustration is furnished by the great glacial grooves at Kelly's 



