CHANNELS AND GLENS OF AYRSHIRE. 59 



glen probably runs from the great scaur— which has slipped so 

 much— near Chapelhouse, in the direction of Aikencleugh. Near 

 here on the south side of the Greenock there are some very old 

 drift landslips caused apparently by springs of water. 



Dippal Bum.— The Dippal, before it joins the Slot Burn to 

 form the Greenock, cuts through rock forming a steep-sided little 

 ferny glen. Above this rocky ravine there is a marine shelly drift 

 extending— on the left side of the burn— to 1061 feet above sea 

 level : the highest point I have found marine shells in the drift 

 {Op. cit. page 80). 



Ponesk Water.— The Ponesk at Cleugh Head wheels round to 

 the left and cuts a deep glen through a felstone ridge. A great 

 peculiarity here is that the hollow between the Ponesk and the 

 Greenock Water is apparently not filled with drift to any extent, 

 and very little damming would send the Ponesk into the Greenock 

 again — its original course. 



When the Ponesk commenced to cut through the rocky ridge, 

 the above hollow may have been choked up with ice from 

 Middlefield Law (see paper by the author in Transactions of 

 the Geological Society of Glasgow. Volume X., 1 896, page 331), and 

 possibly the first river which did the early cutting of this gorge 

 was sub-glacial, as its sides are not so perpendicular as they are 

 in rocky glens of purely river origin. 



Guelt Water.— The Guelt above Whiteholm shepherd's house 

 has left the middle of the old valley, and for a short distance cuts 

 through carboniferous shales and impure limestones, the shales 

 being remarkable for the long lengths of crinoid stems they 

 contain. I once here saw a crinoid stem standing erect in the 

 shale. Above its junction with the Clocklowie Burn, the Guelt 

 cuts through sandstone for a considerable distance, and the new 

 glen appears to cross the old drift-filled one. 



Glenmore Water.— The Glenmore above Dalblair has cut a 

 deep channel in carboniferous rocks, forming magnificient cliffs, 

 where fine slabs of cocks-tail sandstone are to be seen. Above 

 this the glen opens out again and shows the usual scaurs of drift 

 along the sides of the stream. The old valley of the Glenmore 

 is evidently to the east of the new one, beginning below High 

 Dalblair, and ending near Nether Guelt ; the second drift-scaur 



