480 MB. CHAS. DAVISON ON SNOWDKIFT DEPOSITS. [Aug. T894, 



power at mid-day to affect the snow. The surface is thus made 

 soft and sticky, and, during the frost which follows, every crystal 

 receives a thin coating of ice and the snow becomes granular in 

 texture, the optical axes of the grains being of course disposed in 

 every possible direction. As the grains increase in size, the inter- 

 vening air-spaces are more or less filled up, and the surface of the 

 snow is glazed and soon coated with a crust of ice. In the Lower 

 Kolyma district (Siberia) this state of the snow, according to 

 Wrangoll, is called ' Nast.' " The hunters profit by it to pursue the 

 elks and reindeers by night ; and as the weight of these animals 

 causes them to break through, they fall an easy prey." 1 Thaw- 

 water from the surface, however, continues to filter through the 

 capillary passages in the crust, and, meeting with the colder snow 

 below, is again frozen, the whole mass thus becoming granular. 

 " Early in the spring," says Nares, " wherever the stratification of 

 the snow covering a floe had become exposed at a newly-formed 

 crack, the lower portion of the snow was observed to have granulated, 

 the grains collecting together perpendicularly, the lower ones being 

 the largest and leaving intermediate air-spaces." According to obser- 

 vations made by Parr during Markham's northern sledge-journey in 

 1876, " the general depth of the snow was from two and a half to 

 three feet, the upper portion, underneath the surface crust, consisting 

 of loose grains of about the size of rifle fine-grain powder, and 

 without the least coherency ; these gradually increased in size, till 

 about two thirds of the way down they were as large as rifle large- 

 grain powder, but still separate. Below this, however, the grains 

 began to unite and to form very porous ice, till, at the actual point 

 of junction with the floe, it was very difficult to draw the line of 

 demarcation. In all cases the ice on the surface of the floes had 

 evidently been formed in the same manner, for it was full of air- 

 holes, though not nearl) r to so great an extent as that which was in 

 process of formation. ... In one case, also, we found a section of 

 a drift seven feet thick at the highest point, which was divided into 

 three equal parts by two layers of ice half an inch thick ; the lower 

 portion being nearly converted into ice, the middle not to such an 

 extent, while the upper had only just commenced." 2 If, then, the 

 melting take place slowly, masses of snow are in time converted 

 into ice identical, except perhaps in the absence of marked fluxion- 

 structure, with that formed in glaciers. 3 



Snow hardened by the Action of the Wind. — As already remarked, 

 snow at low temperatures is dry and loose. In ravines and under 

 cliffs, where the snow is sheltered from the wind, it remains in this 

 condition, until the sun has power to glaze or melt it. But if exposed 



1 Wrangell, p. 61 (footnote). 



2 Nares, vol. ii. pp. 63-64, 69. 



3 Andree, p. 524 ; Nares, vol. i. pp. 279, 301, 367-68 ; Nordenskiold, vol. i. 

 pp. 136-37 ; Parry S, p. 114; Richardson, vol. ii. pp. 99-100; Eoss, pp. 163, 

 510; Scoresby, vol. i. p. 34; Wrangell, p. 61 (footnote); Whymper, pp. 426- 

 31. See also an admirable paper by F. A. Forel, ' Le Grain du Glacier,' Arch, 

 des Sc. phys. et nat., vol. vii. (1S82) pp. 329-375. 



