486 MR. CHAS. DAVISON ON SNOWDRIFT DEPOSITS. [Aug. 1 894, 



In high latitudes, masses of drift-snow under favourable con- 

 ditions occasionally last through the summer. The deposit formed 

 on the surface by their partial decay serves as an additional protec- 

 tion, 1 the snow that remains having been rendered granular by the 

 re-freezing of infiltrated thaw-water, and perhaps slightly 

 discoloured by the fine particles of dust carried down by it. If the 

 same process is repeated year after year, a mass of ice will be 

 formed, the growths of successive seasons being separated by thin 

 layers of earth or clay. But, in all probability, this will not often 

 occur, and a year of abundant snowdrifting may be followed by 

 others in which the snow disappears more or less completely, and 

 the annual deposits practically coalesce. Now, in Arctic regions, 

 the summer thaw does not often penetrate beyond about a foot in 

 depth. 2 If, then, the thickness of the deposit should ever exceed 

 this limit, it follows that the snow below will not melt so long as 

 the climate remains unchanged. In this way, alternate layers of 

 ice and clay may be built up, the ice corresponding to the snow of a 

 few unusually heavy drifts, the clay being the residual deposit from 

 several or many slighter ones. The remains of animals should thus 

 occur chiefly in the layers of clay ; but, if the theory be correct, 

 they should be found sometimes, though perhaps rarely, in the layers 

 of ice. 



Discussion. 



Prof. Blake asked what necessary connexion snow had with the 

 formation of loess. As far as he could see, the dust could be blown 

 about as well without it as with it, and the deposit might equally well 

 be formed in a tropical climate to-day as during the Glacial period. 



Prof. Boyd Dawkins considered that the word ' loess ' was an un- 

 fortunate term. If the material were called ' loam,' it would at 

 once be realized that loam may be either the result of the wind or 

 of deposit by water, or the work of the earthworm. The mam- 

 moth had nothing to do with the question, because it occurred in 

 the South of Europe and in North America far away from the range 

 of the ' loess.' 



Mr. Oldham said that he happened to have a personal acquaint- 

 ance with the deposits left after the melting of snow and with the 

 loess. The former were found in sheltered spots on the ridges 

 of the Himalayas which are annually covered with snow, but (so far 

 as his experience went) they were denser and more compact than 

 the true loess ; they were in fact dried muds, while the true loess was 

 a dust. On the hills of the Western frontier of India, where loess 

 was largely developed and still in course of formation, the distri- 

 bution, surface-contour, and constitution showed it to be a wind- 



M'Clintock, p. 146 ; Nare3, vol. ii. pp. 12, 13, 47, 66 ; Nordenskiold, vol. i. 

 pp. 378, 436 (footnote), vol. ii. p. 204 ; Parry C, p. 23 ; WrangelL, pp. ciii, 

 cxxxi-cxxxii, 50-51, 222-24, 279. 



1 Nares, vol. ii. p. 66 ; Nordenskiold, vol. ii. p. 61 ; Payer, vol. i.pp. 184-85, 

 251 ; Ross, p. 618. 



2 Nares, vol. ii. p. 77 ; Parry B, p. 124 ; Wrangell, pp. Hi, 38-39, 185, 276. 



