96 GLACIOLOGY 



steeply at angles between 45° and 75°. The water here was unfit to drink, owing 

 to the amount of fine sediment held in suspension. As the stream became sluggish 

 when breaking up into numerous branches and meandering across the alluvial 

 stretches of land at its mouth, this fine sediment could quite easily be observed 

 settling down in sufiicient quantity to add appreciably to the delta even in the 

 course of a few days. 



Stranded Moraines in McMurdo Sound. The moraines are several miles long 

 and of considerable breadth, while many of their numerous small hills reach a 

 height of between 100 and 150 feet. They consist of a heterogeneous collection 

 of debris of numerous varieties of rocks, and the material ranges in size from blocks 

 containing many cubic feet of rock down to the finest dust. They are sejiarated 

 from the piedmont glacier which here fringes the mountains by a stream channel 

 cut out almost to sea-level, and the water which has accomplished this erosion is 

 evidently the result of the summer thaw, the stream being fed during that season 

 both from the glacier and from the snow-drifts on the western side of the moraines. 

 This stream is undercutting the ice, and from the exposures of morainic material 

 on its western bank it appears probable that the mantle of debris continues right 

 up to the flanks of the foothills of the west. 



The debris being mostly of a dark colour the amount of thaw in summer is 

 considerable, and the whole district is seamed with stream-channels which, during 

 the few sunny days in the height of summer, are filled with running water. Every 

 basin-like hollow between the ridges and peaks is filled with a lake of size cor- 

 responding with that of the hollow. In spite of the loose nature of the debris the 

 lake basins are enabled to hold water, because at all periods of the year the ground 

 at a depth of a few feet is frozen hard. Even in the summer the whole mass of the 

 debris, except an outer mantle, is firmly cemented in consequence of the freezing at 

 a slight depth of the percolating water supplied by the melting snow-drifts. 



Proof of this is seen where the streams have cut fairly deep channels in tlie 

 moraines. In the walls of these channels lenticles of opaque ice fairly free from 

 gravel, and varying from an inch or two to a couple of feet in thickness, are to be 

 seen in many places, while in other places, if a few feet of the outer mantle of the 

 stream -clift' are removed, the gravel behind is found to be firmly cemented. 



Most of the streams run northwards, and at the northern end of the moraines 

 quite a thick alluvial deposit, having a strong resemblance to a series of miniature 

 deltas, is to be seen along the ice-foot awaiting subsequent removal to the sea. 

 The amount of material removed from the moraines in this way must be very 

 considerable. Another agency which must be fast reducing the size of the moraines 

 is the direct heat of the summer sun on the cliffs at the northern end. Frequently, 

 while we were camped near the moraines, small avalanches of gravel and mud fell on 

 to the ice-foot, and many tons of material brought down in this manner must be 

 carried away when the ice-foot breaks up in the late summer months. The wind 



