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748
THE POPULAR SCIENCE MONTHLY.

ency to fatten, and animals intended for the shambles have been purposely rotted in order to increase their fattening properties. A celebrated stock-man in England used to overflow his pastures, and, after the water was run off, turn on his sheep which he was preparing for the market. These animals became infested, accumulated flesh rapidly, and by this manœuvre a gain of some weeks was obtained. The practice is certainly questionable, if not positively vicious.

The writer claims no originality in the present paper, and only acts the part—and that imperfectly—of a middle-man in science.

CYCLONES AND TORNADOES.

By GEORGE CLINTON SMITH.

CYCLONES.

TOWARD the western portion of the United States, along the twenty-fifth parallel of longitude, lies a vast tract of sandy, arid country, known to the earlier geographers as "The Great American Desert." It is true, the limits of this great area have become circumscribed by the onward march of civilization, but the sandy waste is still there, and must ever remain. Still farther westward, the Rocky Mountains rear their lofty, snow-crowned heads in one continuous chain, three thousand miles in length. Rich in mineral wealth, the delight of tourists, and the home of a prosperous people, these mountains have a different and equally valuable office to perform in the exercise of an important influence upon the climate of our continent. Were they to be removed, the entire territory west of the Mississippi River would soon become an arid, lifeless desert.

All storms, of any magnitude, that visit the United States, except the tropical hurricanes which sometimes touch the southern coasts, have a common origin in or near the Rocky Mountains. Here the first barometric depression is felt, preceded by a rising temperature, caused by the warm winds moving northward over the sun-heated sands of Arizona, New Mexico, and Western Texas. These warm, rarefied currents of air are met by cooler currents passing over the snow-clad peaks of the north; a cyclonic storm is formed, usually small at first, which begins its journey eastward, gradually developing in energy and area as it goes. After leaving the mountain-ranges, there is but little precipitation for the first few hundred miles; as it advances, it usually widens from north to south, but the line of travel of the storm-center can be readily predicted by the Signal-Service observers, and its location at any time fixed by the lowest reported reading of the barometer.

During the journey of the storm eastward or southeastward, the