THE CLYDE DRAINAGE AREA. 525 



short distances, or even on the same rock-surface) so that the bulk of the 

 evidence is in favour of their having been produced by the action of land-ice, 

 before the drift-beds were deposited, but some of them may have been 

 caused by icebergs during a depression of the land. Striae occasionally 

 ascend on rock -surf aces, as in Bute, at Ashgrove near Stevens ton, in Dun- 

 nach Burn, Ballantrae, 1 in Loch Doon, and in the Afton valley. 



ROCK-DRUMS. 



In the low grounds rock-drums often occur, probably under drift, and 

 near the coast examples are sometimes laid bare, as at Bennane Head, N. of 

 Ballantrae. In the valleys hemmed in by steep-sided hills especially where 

 the rocks are of unequal hardness 2 they are very numerous. Perhaps the 

 finest display of them in the Clyde area is on the hill-slopes in the lower 

 eastern part of Noddsdale, and in the upper part of the Girvan valley. On 

 the moors they are abundant, and permanently wet rock-faces often have 

 them very well preserved. The long axes of rock-drums are usually with 

 the striae. 



DRIFT-DRUMS. 



The 60-feet and 40-feet Eaised Beaches occasionally rest on Boulder-clay 

 drums. Up to 800 feet above sea-level there are immense numbers of drift- 

 drums, their long axes being generally with the valleys, but sometimes across 

 them. Above that height clusters of small drift-drums occasionally occur in 

 the narrow valleys and usually at the junction of a side valley with a larger 

 one. 3 It is quite evident that many at least of the drift-drums have been 

 carved out of stratified deposits by glacier-ice. 4 A drift-drum is sometimes 

 found resting on top of a rock-drum. The waves during the last Eaised 

 Beach period truncated the large drift-drums N. of Girvan and Ballantrae, 5 

 and drift has in many places, like beds of rock, been entirely carried away by 

 glacier-ice. 



MORAINES. 



These remains of ice-action are singularly scanty. Some of the fishing 

 " banks" in the Clyde estuary may be the upper surfaces of either moraines- 

 or drift-drums. At low levels near the mouths of some of the Highland 

 glens a few occur, like the remarkable one near Row ; on Loch Lomond-side 

 N. of Balmaha ; and in Arran. The fine example in Glen Fruin has a ground 

 plan of nearly semicircular outline, with a length of about 4 miles, and 

 climbs the hills on either side to a height of several hundred feet. 6 There 

 are also the Colmonell moraine 7 ; the Cuff hill moraine ; the Penwhapple,, 

 Polreoch, and Avon moraines, about 750 feet above sea-level. 8 



KAMES. 



Carnwath is the great centre for the peculiar accumulations of stratified sand 

 and gravel which are known as kames. There they present the appearance 

 of a " tumbled sea . . . the ground now swelling . . . into beautiful peaks 

 and cones, and anon curving up in sharp ridges that often wheel suddenly 

 round so as to enclose a lakelet of bright, clear water." 9 Somewhat similar 

 surface-features are to be found near Maybole. Some kame-like hillocks of 

 drift are probably due to recent river-denudation, as near Skelmorlie ; in 

 the angle between the Avon Water and the Glengavil Water ; and near 



1 Trans. Geol. Soc. of Glasgoiv, vol. xi., supplement, p. 68. 2 Ibid. t p. 104, fig. 42. 



3 Ibid., pp. 45, 101, 102. *Ibid., p. 16, fig. 4. * Ibid., p. 118, fig. 49. 



6 Renwick, Trans. Geol. Soc. of Glasgow, vol. x., 1895, p. 96. 



Ubid., vol. xi., supplement, p. 19. *Ibid., pp. 66, 67, figs. 29, 30, 31. 



9 J. Geikie, Great Ice Age, 3rd ed., 1894, p. 181. 



