Page:Popular Science Monthly Volume 13.djvu/135

Rh open shallow well or spring, and had become very tame. In the well was a flat stone, one end of which projected above the water. On this small birds would alight to drink, and the villagers suspected that more than one of them had fallen victims to the trout's rapacity. This surmise proved to be correct, for, one day while the owner of the well was passing with some friends, a splashing in the water caused them to turn and look. There was the trout struggling hard to gulp his prey. One of the spectators fearing that the fish would be choked by the wing feathers, thrust his hand into the water, and caught hold of them. But the trout, unwilling to surrender any part of his prize, held on resolutely, and the feathers had to be taken from him by force.

Meteorological.—In the eighth of Prof. Loomis's papers on Meteorological Phenomena, published in the American Journal of Science for January, with a view to determine the circumstances under which storms originate, the author takes all the instances in which the barometer fell below 29.25 inches at any station, Mount Washington and Virginia City excepted, during a period of twenty months from September, 1872, to May, 1874. The number of instances was 148, and corresponds to 44 different storms. Two-thirds of these storms had their origin north of latitude 36°, and one-half upon or very near the Rocky Mountains. Two of them came from the Pacific Ocean, three from the Gulf of Mexico, one from near Cuba; others were widely distributed in Wyoming, Dakota, Colorado, and elsewhere. The first stage in each of these storms was the development of an area several hundred miles in diameter, over which the barometer was about thirty inches, with areas of high barometer on both the east and west sides, a thousand miles distant. These areas of high barometer are one of the most important causes of the storm which succeeds. From this cause there arises a movement of air toward the central area which is relatively one of low barometer. The air thus in motion is deflected to the right by the earth's rotation, giving rise to the well known rotary motion of air during a storm's progress; there also occurs a diminished pressure in the central portion, and an upward movement of the air. The upward-rushing air carries with it large amounts of aqueous vapor which is condensed into rain. By the condensation of the vapor, heat is liberated, causing expansion of the air, and more violent inward movement of the wind. The rainfall thus tends to increase the force and violence of the storm, and invariably occurs when the storm is at its height. Heavy rains usually occur eastward of the storm-centre—that is, eastward of the area of lowest barometer—and usually diminish when the centre has passed. The author says, "I have found no instance of violent storms which was not attended by considerable rainfall, but the rainfall is to be considered as a result, not the cause of the first movement of the wind."

It was shown, in a former article, that storms have a forward motion, which is usually a little north of east. No sooner is a storm-centre formed than it begins to change its position. The storm's movement seems, with few exceptions, to correspond with that of the atmosphere, the average annual progress of which is from west to east. Prof. Loomis says that on the west side of a storm a pressure occurs, resulting from the cause which determines the general circulation of the atmosphere, and which exists whether a storm occurs or not. A storm disturbs the atmosphere chiefly in its lower portion; in the upper portions the general atmospheric movement goes on. The depressions of the atmosphere on the west side of a storm are from these conditions filled up, so that the barometer is continually rising closely in the rear of a storm, but as continually falling as before explained, just eastward of the storm-centre. It is a matter of common observation that, when a storm-centre is passed, high barometer and clear air are close at hand. Other conditions of a storm's progress are presented, and the interesting fact developed that high barometer, east and west of a storm-area, remains unaffected by the tempest that is raging between those areas—whence Prof. Loomis infers that the air inflowing in the storm and rising at or near its centre flows outward at a considerable elevation to the areas of high barometer, having been deprived of its aqueous vapor. It thus appears that a vertical circulation is going on during a storm's progress.