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U. S. ASTROPHYSICAL OBSERVATORY, WASHINGTON, D. C. Building at extreme right is the Smithsonian Institution.

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of air, Mr. Abbott finds the rate at which the sun is actually throwing off heat. This rate varies independently of the change in our atmosphere; and its variations-which are more or less irregular -are probably caused by a greater or less permeability of the sun's own atmosphere. These variations generally occur only two or three times a year, as already said; and once this change is definitely noted, it may be as safe to predict a radical change in an entire season-whether it will be unusually cold or wet-as it now is to forecast a change of local weather for a mere day.

Few of us realize the enormous bulk of the sun. If it were hollowed out and

equally bright all over, but is slightly darker toward the edges. This is because the great orb has a gaseous envelope or atmosphere which at the edges acts like our own atmosphere at sunrise or sunset, when the latter intercepts more light than at noon. This envelope is of the greatest consequence to us, and regulates for our use the heat of the sun, upon which is dependent every earthly thing that has life. Were this gaseous solar covering removed, our sphere would be unfit for habitation. We should all frizzle up.

At times this envelope of atmosphere about the sun becomes hazy, much as does our own atmosphere. When it is

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pecially near the edges, little bright spots called facula. They are brighter than the sun itself, and are supposed to be caused by metals glowing as they melt and boil. At other places on the great orb are seen spots darker than the remainder of the surface and moving among themselves like clouds. These "sun spots," supposed to be holes in the solar surface, are often of enormous size -so large, in fact, that the whole earth might be dropped into the center of one "like a pea into a thimble," as Professor Langley used to put it. In 1903, when the Astrophysical Observatory estimated a fall of from 10 to 13 per cent of the

system as soon as it shall have been perfected. At its new research observatory on the summit of Mount Weather, Virginia, it is preparing for the installation of apparatus similar to that used by Mr. Abbott. A Weather Bureau man has been in training for some months at the Astrophysical Observatory, in order to master the methods exactly.

The Mount Weather Observatory is an institution unique in the western hemisphere. It occupies a high crest of the Blue Ridge mountains, in the upper corner of Virginia, very near the West Virginia line, and overlooks not only the beautiful Loudoun valley on the east, but

the superb Shenandoah on the west. The instrument equipment includes devices such as described, and also apparatus for measuring the electricity in the atmosphere, for studying the relations to the atmosphere of the magnetism of the earth, the temperature of the soil, and even the motions of the earth-all of these phenomena being suspected of having a more or less intimate connection with the weather.

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Adjacent to the main observatory building are two magnetic observatories, known as the "Absolute" and "Variation" buildings, respectively. Here the mysterious relations of magnetic storms, earth currents, and such phenomena, to sun spots, the aurora borealis, atmospheric electricity, and weather in general, will be carefully studied. "kite house," another interesting adjunct, is a shingled, cylindrical structure -a sort of Dutch windmill tower-flattened on one side, where appear two pairs of doors, one above the other. Out of the roof extends a tube through which will be passed the wire cable holding the large box kites to be used in exploring the atmosphere at levels below those visited by balloons. Inside of the tower is a large reel governing the kites. The largest of the Weather Bureau box kites, measuring 72 feet wide by 62 feet high

KITE TOWER, MOUNT WEATHER OBSERVATORY.

and 32 inches deep, has, with recording instruments attached, soared to a height of nearly a mile and a-quarter, probably as high an elevation as ever attained by an independent kite of any pattern.

The Weather Bureau will here strive also for longer range in forecasting local as well as general weather conditions. This is expected to result from thorough exploration of the upper air as far as balloons can venture. "Sounding balloons" will be exploded in many parts of each great storm that enters the conti

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a-quarter miles up, he swooned away. Dr. A. Berson, who in 1894 ventured as high as five and two-thirds miles, commenced breathing pure oxygen when he had made less than four and a-quarter miles, his heart having commenced to beat and ache violently when he had covered but a little over two and a-half miles. Bersch and Snering, Germans, who made an ascent in 1901, fainted at six and fourtenths miles. Thus it will be seen that no creature of flesh and blood could survive to the tremendous height of twenty miles, anticipated by Professor Moore.

BOLOMETRIC LABORATORY, MOUNT VILSON OBSERVATORY.

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Even were the feat possible, there would be small advantage in dispatching a man to such an altitude. In this bright age, mechanical agencies perceive even more accurately and acutely than the sense organs of man; and such a device -the "meteorograph"-capable of serving as a substitute for both an aëronaut and a weather observer, has been perfected by Prof. C. F. Marvin of Chief Moore's staff. With four fountain pens, it automatically keeps continuous record of temperature, pressure, wind velocity, and moisture, as the balloon to which it is attached continues its ascent; and yet, such is its compactness that it weighs. but two pounds and occupies a space no. greater than that of an ordinary hand camera. To produce an ink which will not freeze, however, will be a rather difficult problem, since at an altitude of only seven and three-quarters miles, the fluid. in the registry pen of the thermometer carried by an unmanned balloon sent up by the French scientists Hermits and Besançon became a mass of ice. The thermometer showed 51 degrees below zero, Centigrade, when the ink froze.

For ascents of twenty miles, it might be preferred to send up in tandem two balloons filled to different degrees with gas, so that, after the bursting of the larger, the other-weighted down by the exploded envelope-would bring the apparatus gradually to earth, at the same

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