The Recent Irish Glaciers. 237 



cliffs great snow- drifts accumulated, from fifty to hundreds of 

 feet in depth, and often from 200 to 500 or more yards wide. 

 These drifts had certain defined limits, due to shoulders on 

 the hill slopes that acted as groins, behind which the snow 

 was impounded. After the snow-fall ceased, the surface of the 

 drifts melted and froze ; so that after all the snow elsewhere 

 had disappeared, these drifts still remained, often for months. 

 As is always the case after a severe frost, blocks and other 

 detritus are displaced by falls when the thaw conies on ; and if 

 the fall is from a cliff over one of those drifts, the blocks and 

 other stuff slide over it and form round its edge a terminal 

 moraine. After a severe winter this phenomenon can be 

 studied in the month of March, in the Co. Wicklow, at the 

 North and South Prisons, Slieve-na-calliagh, and in the coom 

 west of Kelly's Lough ; as in these places, great and long 

 enduring drifts form during any heavy snow-fall. These 

 snow-drifts nearly invariably disappear in as sudden a manner 

 as they were formed ; they may last for weeks or months ; but 

 when the ground gets to a certain temperature all go at once. 

 About the year 1870 there were great snow lakes in the 

 valleys of the tributaries of the Ovoca ; and the snow barriers 

 all burst nearly at the one time — at mid-day early in June, 

 flooding the whole valley and carrying away the bridges. 



Those who wish to study this phenomenon should visit the 

 hill districts when in deep snow, and thereby learn the localities 

 of the deep and lasting drift, and afterwards visit them in the 

 subsequent thaw, and see the stones sliding over them as they 

 break loose. 



Under a cliff on L,issoughter, Co. Galway, there was such a 

 drift/that I was going to cross in the thaw when out shooting, 

 but my man advised me not to do so, for although the snow 

 was quite safe, blocks might come down ; he, at the same time, 

 pointing to a mass that he said was loose ; this broke away 

 and slid over the glacier before we left the spot. A stack of 

 blocks in Glen Inagh over which I was puzzled led me to visit 

 this valley at this time. Here about 200 yards from the cliff 

 there was an isolated stack ; on visiting the place in snow I 

 found, under the nearly perpendicular cliff margining the valley 

 to south and west, there was one of those frozen snow-drifts, 

 while near the centre of it was a valley between the peaks 

 called Benbawn and Bencorrbeg. Down this valley, in 



