THE HEART OF THE ANTARCTIC 



at a temperature between 28° and 29° Fahr., causing 

 actual thawing of the drift to take place from below and 

 the ice-crust over the top of the drifts to become much 

 thicker. The thickness in cases of deep drifts attains as 

 much as a quarter of an inch. When this crust breaks 

 beneath the foot, an unwary explorer is liable to be let 

 down six or nine inches into a pool of salt water several 

 inches deep, and this rendered sledging over the sea ice in 

 the late summer particularly objectionable. 



On December 21 the temperature of the air in the 

 Ferrar Glacier Valley reached 40° Fahr., and in the few 

 hours during which the air remained calm two inches of 

 snow which had fallen the previous night had either been 

 entirely removed as thaw-water or converted into a thin 

 coating of rough ice, opaque through the inclusion of 

 air, which formed a distinct help to us in our subsequent 

 marches, as it very much reduced the slipperiness of the 

 ablation ripples. 



The principal chai'acteristics of this big thaw on an 

 Antarctic glacier are interesting, and some of them may 

 be mentioned here. Every stone in the glacial moraines is 

 surrounded by a large hollow, scooped out by the heat 

 radiation from the boulder, and these hollows are all, more 

 or less, full of thaw-water, which is also overflowing 

 through every deep ablation ripple and crack. A number 

 of the small rivulets from these sources join up at a little 

 distance from their source to form a stream, and innumer- 

 able streams are flowing down over the convex face of 

 the glacier to join the river which can be heard roaring 

 at the foot of the clifl* which ends the ice-face. In search- 

 ing for a camp on the night of the 21st we passed across 

 large areas of the glacier face which were slightly de- 

 pressed below the general level and at the bottoms of these 

 depressions we were compelled to wade through stretches 

 of water, three or four inches deep, for hundreds of yards. 



352 



