THE CLYDE DRAINAGE AREA. 523 



exposed within a few yards, at about 380 feet above sea-level, and dip 

 with the valley at about 80 . 1 



Passage-beds from Boulder-clay to Sand are well seen on Changue Burn, in 

 Galston parish, 700 feet above sea-level. 



Peat and Vegetable Matter in Drift are found : under a sand-bed in Boulder- 

 clay at Gamesloup, 70 feet 2 ; at Burnhead, near Airdrie 3 ; in sand under thick 

 Boulder-clay on Guelt Water, at 860 feet above sea-level 4 ; on Patrick Burn, 

 Muirkirk, in Boulder-clay and resting on a rotted surface of the same material, 

 at about 1000 feet above sea-level ; ou Afton Water, but doubtfully if in 

 situ, at 1350 feet above sea-level. 



Shore-lines and Gravel Terraces. Near the " Windy Wizzen," E. of Darvel, 

 the officers of the Survey have shown on the 1 inch map No. 22, "an old sea- 

 beach about 700 feet above sea-level." Lately, I saw that, where exposed, 

 large blocks of trap from the great scar on the south face of London Hill had 

 at one time rolled down on the top of this sand and gravel deposit, so that 

 this cliff may have been the work of the waves helped by floating-ice. 

 Terraces of sand and gravel occur near Eagleshain 535 to 900 feet above sea- 

 level, 5 and among the Moorfoot Hills at 1050 to 1100 feet. 6 Where Boulder- 

 clay has been denuded away, sand and gravel are often exposed on the surface 

 over small areas, as on the Annick Water at 620 feet above sea-level, where 

 they may be seen going under Boulder-clay. 



Hill-Benches backed by Cliffs or Banks &TZ occasionally seen at London Hill ; 

 Glen, near New Cumnock about 900 feet above sea-level ; Ponesk Valley, 

 Muirkirk, at about 1300 feet 7 ; and in many places to much higher altitudes 

 un the hills near the higher tributaries of the Clyde. 



Old Drift-filled Glens are frequent, the rivers having at many places left 

 their old glens and cut new ones, often out of solid rock. 8 



Post-Glacial Glens cut in Rock. Examples of these are : the Mouse Water, 

 Lanark ; Craignethan ; Ness Glen, Loch Doon ; Boreland Glen, near Patna ; 

 Hindog Glen and Cleaves Glen, Dairy ; and the gorge in the Permian rocks 

 near Barskimming. 



Old Land-Surfaces have been found in the drift 300 to 400 feet above sea- 

 level, near Beith, with roots of oak, hazel, and other trees, between Boulder- 



clays. 9 



Angular Blocks. In the moraine of the Ford of Moak, Loch Doon, there is 

 a great assemblage of angular blocks, which to all appearance have never 

 been rubbed, and were probably carried on the surface of a glacier. 



Dry River Channels occur near Muirkirk, New Cumnock and Ballantrae, 

 and are cut out both of rock and drift. They have probably been formed by 

 streams diverted from their normal courses by ice -dams. 10 



BOULDERS. 



According to the late Mr. Allport there is not a boulder in Arran foreign 

 to the island, and although it is a strong statement I know of no contradictory 

 evidence. The principal carriage of the granite blocks has been S. and towards 

 the Atlantic, very few having, apparently, come E. Across the Firth of 



1 Ibid., p. 38, fig. 15. 2 /foW., p. 12, fig. 2. 



3 Ibid., vol. viii., part 2, 1888, p. 312. 



4 Ibid., vol. xi., supplement, p. 73. 



5 James Geikie, Great Ice Age, 3rd ed., 1894, p. 175, fig. 46. 

 *lbid., p. 177. 



7 Trans. OeoL Soc. of Glasgow, vol. xi., supplement (referred to in Index). 



8 See paper by the author on "The Buried or Drift-filled Glens and Channels ; and the 

 Post-glacial Glens of Ayrshire," Annals of the Anderson ian Naturalists Society, vol. ii., 

 pp. 51-66. 



9 R. Craig, Trans. Geol. Soc. of Glasgow, vol. iv., part 2, 1873, p. 138. 

 10 Trans. Geol. Soc. of Glasgow, vol. x., part 2, 1896, p. 331. 



