GLACIOLOGY OF THE SOUTH ORKNEYS. 841 



Surface Slopes. — The general surface of the ice-sheets is an undulating one, and 

 evidently conforms fairly closely with the underlying ground — more so in some places 

 than in others, — but so far as was seen, with one exception, the slope is always down- 

 wards in the direction of flow. This exception is in the case of the ice-sheet at the 

 base of the west side of Pirie Peninsula, where there is a slight reverse slope near the 

 termination. There must be some rising ground underneath, for the ice is much 

 crevassed. The glacier as a whole may be travelling uphill for a distance of several 

 hundred feet, but the total rise on the upper surface does not, I think, exceed 20 feet. 

 It was not possible to measure it exactly. 



Crevasses. — Generally speaking, crevasses are rare in this portion of the ice-sheets 

 save in cols and when approaching the terminal ice-cliff, and even in the latter situation 

 they are comparatively insignificant in size. The crevasses are nearly all transverse 

 in their direction. Longitudinal crevasses (or cracks, rather, for they were scarcely 

 open) are to be seen in the " Half-Moon Glacier," on the west side of Scotia Bay (see 

 Plate v.). Possibly they would be found in other situations if the surface snow 

 disappeared to a sufficient extent to enable them to be seen. During the winter the 

 crevasses are nearly all bridged over by snow, and even in summer many of them are 

 also, so that they may really be more numerous than appears. 



Snow A.cctjmulation. 



The conditions of precipitation and accumulation at the South Orkneys are not 

 quite the same as those described by Nordenskjold at Snow Hill, where he says (18) : 

 " Aucun d^pot de neige ne s'est produit en hiver. Aussitot tombee, la neige etait 

 balayee par le vent. Au contraire, durant I'ete 1902-3, le revetement de neige 

 augmenta notablement, d'environ 0"30m. a 0"35m., et, en novembre 1903, lorsque nous 

 avons quitte la station d'hivernage, cette augmentation persistait." At Wandel Island, 

 according to Gourdon (19), the precipitation occurs chiefly in spring and summer. 



At the South Orkneys, although it is perfectly true that the frequent and violent 

 winds do sweep a great deal of the snow which falls in winter off" the glaciers on to 

 the ice-floe, still a very considerable proportion of the winter's fall is here retained for 

 reasons given below. 



According to Mobsman (see p. 835) about 40 per cent, of the precipitation at the 

 South Orkneys occurs during the summer months, December to February, but accumu- 

 lation on the glaciers, as judged by the depth of the surface layer of snow, is certainly 

 not at its maximum during this period. A series of measurements was taken of the 

 snow depth at a point near the top of the ice-snout ending on The Beach. This place 

 was freely exposed to wind and sun, and the accumulation there in the winter was 

 probably less than in many places, although, on the other hand, the melting there in 

 summer was, from observation, distinctly greater than in most places. The results at 

 this spot were as follows :— On 5th May 1903 a measuring peg was set up ; at this date 



