Waves of sand and snow and the eddies which make them . ation of the view I had already advanced, thatwaves in granular material do not require for theirformation the existence of an eddy-making obstruc-tion, as was formerly held, but inevitably originateupon an unobstructed surface from the silting andscouring action which is exercised when the wind(blowing as it always does with variable velocity)has a speed, even in the lulls, sufficient to pickup the particles, which must be themselves of sucha density and size that they do not follow the linesof flow of the air, but subside at an apprecia
Waves of sand and snow and the eddies which make them . ation of the view I had already advanced, thatwaves in granular material do not require for theirformation the existence of an eddy-making obstruc-tion, as was formerly held, but inevitably originateupon an unobstructed surface from the silting andscouring action which is exercised when the wind(blowing as it always does with variable velocity)has a speed, even in the lulls, sufficient to pickup the particles, which must be themselves of sucha density and size that they do not follow the linesof flow of the air, but subside at an appreciablerate. Crescentic Snow-waves or Snow-bar chans. When there is only a small amount of loose, drysnow drifting over a hard surface it does not accu- 114 WAVES OF SAND AND SNOW mulate in transverse ridges but in low, narrowmounds, having on the lee a cliff, which is highestin the centre and projects forwards on either sidein horns or cusps. The shape is that of thecrescentic sand-dunes known as medanos orbarchans, but with finer lines, the snow-barchan. Fig. 6Barchans of snow and photographs. being both narrower and flatter (Fig. 6). I sawmany hundreds of these structures which had beenproduced in ordinary fresh-fallen dry snow, butin the absence of any steep eminence to give mea good view-point I was unable to obtain a photo-graph showing how the prairie was dotted overwith these structures.
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Keywords: ., bookcentury1900, bookdecade1910, bookidwavesofs, booksubjectwaves
