ICE-EROSION IN THE CUILLLN HILLS, SKYE. 



239 



condition in both cases was the same, a marked constriction of the valley towards its 

 lower end, which must have occasioned a certain heaping up of the ice in that part. 

 In Coruisk the constriction was caused by the Sgurr Dubh ridge running out eastward 

 from the main range ; in the Camasunary valley the same effect was produced by the 

 convergence southward of the flanking ridges, Blath-bheinn on the east and Druim an 

 Eidhne, Sgiirr an Eidhne, and Sgurr na Stri on the west. The third main valley, 

 that of Sligachan, opens out towards its lower end, and there is accordingly no 

 rock-basin. 



With the kind co-operation of Mr T. A. Falcon, a series of about 150 soundings 

 have been taken in Loch Coruisk, and the results are embodied in the rough contoured 

 map given in fig. 8. Owing to practical difficulties,* the soundings are rather deficient 



sa I CONTOUR LINES 



T S DEPTH III FEET 



100 J 



-©»■ &L«CI»L STRI/E 



SHINGLE DELTAS. 



Fig. 8. — Bathymetric map of Loch Coruisk, plotted from 150 soundings taken by T. A. Falcon and A. Hakker. The 

 actual soundings are given only in places where the contour-lines alone do not suffice to render the form of the bottom. 

 The water-surface is 26 feet above sea-level. 



in places, and unfortunately so in the deeper part of the loch ; but the general form 

 of the bottom is rendered with sufficient accuracy for our purpose. It will be seen 

 that there are in reality two basins, the maximum depth being nearly 90 feet in the 

 upper one and 125 feet in the lower, which latter goes nearly 100 feet below the 

 sea-level (O.D.). These two basins are separated by a shallower area, never exceeding 

 40 feet in depth and rising in several places into small islets. The bottom is in 

 general of bare rock. The shallow head of the loch is partly filled by a flat shingle 

 delta, and the bottom is also shingly in places along the south-western shore ; but these 

 accumulations are nowhere in such force as to prevent the soundings giving very closely 

 the true shape of the rock-basin. This seems to differ in no respect, as regards detailed 

 sculpture, from the shape of the valley bottom where it does not happen to be covered 



* The principal difficulty was in finding sufficiently calm weather. In a wind it was found impossible to keep 

 the boat in place while a sounding was made and the position determined. 



