THAW 203 



of 1908, the snow, 2 feet from the rock, was converted into a coarse-grained neve, 

 graduating into ice as the rock was approached, and before the end of November 

 a small rivulet was seen flowing from underneath the drift, whilst the surface, except 

 near the edges, seemed to have remained comparatively unaffected. 



At Cape Royds, as observed at the Stranded Moraines later on, there was a 

 periodicity in the thaw which was not governed by the amount of sun's heat so 

 much as by the complete, or almost complete, removal of the smaller snow-drifts, and 

 the necessary lull until the snow-drifts had been renewed by a drift-laden blizzard or 

 a snowstorm. Our observations of thaw at Cape Royds are naturally somewhat 

 incomplete, as after December 1, 1908, there was no geologist left at the winter 

 quarters. 



It is quite a common thing for snow-drifts to melt quite quickly on slopes exposed 

 to the summer sun, and for the thaw-water to become frozen when it reaches a 

 hollow where the sun has no direct effect. 



A well-marked example of this, much exaggerated by circumstances, was seen 

 when the snow-drift on the ridge at the back of the Hut commenced to melt in 

 December 1908. The thaw-water which ran below the house, where the sunshine 

 could not penetrate, and the air temperature never rose above 32° F., froze at once, 

 and never again thawed. Each day's thaw added another layer, until the snow- 

 drift had disappeared entirely from the hill, and there was a pool of ice 18 inches to 

 2 feet deep below the Hut. 



We are indebted to our biological colleague, Mr. James Murray, for the following 

 information in regard to the summer thaw of the lakes at Cape Royds : — 



SUMMER THAW OF THE LAKES, CAPE ROYDS 



Accounts have already been given, in Chapter V., of the thaw observed by the 

 Western Party in the Ferrar Glacier Valley, and the thaw-water streams are 

 illustrated in Plate XVIH. Fig. 1 and Plate XIX. Fig. 2. 



1908. 

 Oct, 13. No open water in any lake. 

 Nov. 4. Clear Lake. A few inches of water lying on the ice in narrow zone along the black 



rocky ridge. 

 Nov. 14. No open water at any lake. 



Nov. 28. Blue Lake, pool at the Nai-rows (never thawed further), Pony Lake, several small pools. 

 Nov. 29. Green Lake, thawing at edge. 

 Nov. 30. Blue Lake. Pools on the ice at margin formed by thaw-water running down from drifts. 



Coast Lake, melted at edge. 

 Dec. 11. Clear Lake. No melting except narrow band round the island which you could step 



across. (This lake never thawed more.) 

 Dec. 13. Pony Lake, tlu-ee ponds formed, the largest at hut; overflow by two streams, one going to 



the Rookery and the other to Arrival Bay. 

 Dec. 29. Green Lake and Coast Lake, about half melted. 



