114 Proceedings of Royal Society of Edinburgh. [sess. 
Conclusions . — I have here dealt with two examples of rock basins 
or corrie lakes. Now, if small corrie glaciers have been able to erode 
rock basins, a fortiori the tremendous valley glaciers would erode 
rock basins. In my opinion the erosive action of a glacier is not 
only due to the pressure of the ice on its bed, but also to the action 
of the water running over the bed ; for the water will fill up the 
Fig. 4. — Lake of Yogealle. 
cracks and fissures of the bed, and, in certain seasons when freezing - 
and melting take place, will be a powerful agent of disintegration. 
It is a fact well known to mountaineers and climbers that the 
water running underneath the glaciers during the day freezes during 
the night at the end of the summer and in autumn, cutting off the 
supply of the streams originating therefrom. That fact is worth 
noting, because many antiglacialists say that a glacier is a protecting 
cover on the rocks. 
As a heading to chapter xvi. of his book Ice or Water , Sir 
