Page:Popular Science Monthly Volume 45.djvu/46

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34
THE POPULAR SCIENCE MONTHLY.

Fig. 6, the accumulation on the tip of a blade of grass, seven eighths of an inch long. This fragment was broken off and brought into the house to show how all the grass was decorated by the storm of January 6th, with wind at forty miles an hour and temperature twenty degrees below zero. It was two inches and three quarters tall and weighed three quarters of an ounce avoirdupois, or more than five thousand times as much as the bit of grass inclosed by it. It was composed of ten large feathers, with the spaces between them filled with smaller ones — no shapeless snow about it. The tips of twigs, ends of fence rails, etc., projecting toward the wind, were all similarly decorated, but on different scales, according to their size and exposure.

Many curious and apparently contradictory effects are produced by the rebound from one surface to another. A post which

PSM V45 D046 Leeward ice plume formation on a bowl in freezing wind.jpg

Fig. 7.

stood twenty feet from the house, in a small court inclosed on three sides, had a deposit on the face toward the house equal to that on the windward side, while the other sides were bare and dry.

Fig. 7 shows a wreath of plumes averaging six inches in length, formed altogether upon the leeward side of a tub, by the rebound of the vapor-laden wind from a high wall about three feet distant. It will be seen that the rebound from the tub again has produced a second series of forms around it on the ground, pointing toward the tub.

The most conspicuous and noteworthy example of this resili-