Waves of sand and snow and the eddies which make them . e snow-waves would, I think,when broken up form snow-sand capable ofrippling, and I have explained how this mightperhaps be produced without melting and re-freezing. On the afternoon of January 25th on the prairienear Winnipeg much of the snow-sand was drift-ing low over the hard, unlevel surface of the oldsnow, never rising more than a few inches abovethe ground. The temperature was about zeroFahrenheit, and the wind had a velocity of 27 milesan hour—/.^., that of a strong breeze. Thelow sun, casting shadows from the steeper leefaces, th
Waves of sand and snow and the eddies which make them . e snow-waves would, I think,when broken up form snow-sand capable ofrippling, and I have explained how this mightperhaps be produced without melting and re-freezing. On the afternoon of January 25th on the prairienear Winnipeg much of the snow-sand was drift-ing low over the hard, unlevel surface of the oldsnow, never rising more than a few inches abovethe ground. The temperature was about zeroFahrenheit, and the wind had a velocity of 27 milesan hour—/.^., that of a strong breeze. Thelow sun, casting shadows from the steeper leefaces, threw the ripples into relief. The drift-ing snow-sand accumulated in the shallow de-pressions in the surface of the old, hardenedsnow. These deposits quickly fell into increase of their wave-length was morerapid than that of aeolian sand-ripples, andtheir motion was also more rapid. In one of thesepatches of snow-sand, ripples having a wave-lengthof 9 inches advanced that distance in i minute50 seconds—, at the rate of 49 inches per. ^ 123 SNOW-WAVES AND SNOW-RIPPLES 125 minute, whereas the aeolian sand-ripples of thesame wave-length which I observed in 1896travelled under the action of a wind of the samestrength at the rate of 0-5 inch per minute. For a time all the ripples in the above-mentionedpatch of sand-snow grew pari passu, each rippleof the group having approximately the same lengthand height, but after a time this state of affairssuddenly changed, the rear ridge—that is, the onemost to windward—beginning to increase in heightvery quickly. I think the change began as soonas the patch of drifted snow-sand rose above thelevel of the surrounding hard surface. When thewindward ridge raised its crest above the others Isaw that the wind eddied in its lee, and observedthat some of the snow-sand in the centre of thepatch was travelling backwards towards the weatherridge. The other ripples, hitherto so sharplydefined in the low sunlight, became indistinct
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