Page:Popular Science Monthly Volume 92.djvu/900

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��Popular Science Monthly

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��-►DIRECTION OF SUN

��EARTH

��MOO;N 5 SHADOW

��MOON

��This diagram, drawn to scale, shows the earth, the moon and the moon's shadow during the echpse. The distance of the sun is 390 times the distance between earth and moon

��have had the privilege of welcoming scores of astronomers from Europe. One large American observatory — the Cham- berlin Observatory, at Denver — will not need to send out an expedition, as it is situated right in the path of totality. The unusual length of this path within accessible territory is a particularly favorable circumstance, for the reason that observers at western stations, after viewing the eclipse, will have ample time to telegraph to those at eastern stations, calling attention to any features that especially demand further observation.

By hiding the sun and cutting off the glare of sunlight in our atmosphere, an eclipse makes it possible for us to see the envelope of incandescent gases by which the sun is surrounded, known as the chromosphere. Beyond the chromosphere, and extending millions of miles into space, is a pearly white glow, of irregular

��outline, known as the corona. By means of a marvelous instrument called the spectroscope astronomers are able to see and to photograph the chromosphere and its prominences at any time; but the corona can never be observed except during a total eclipse. The spectroscope is also applied, while an eclipse is in progress, to a study. of the chemical composition and the movements of these solar envelopes or atmospheres.

In past eclipses eager search was made, by photography and otherwise, for a possible planet, or planets, lying within the orbit of Mercury — the nearest to the sun of the planets now known — and ob- servations of an "intramercurial planet" were occasionally reported. These ob- servations were, however, undoubtedly erroneous and astronomers the world over have generally given up hope of find- ing such a planet.

���About eighty-five towns are directly in the path of the total eclipse. Since we are saving daylight add an hour to the times on the map. The track of totality extends from Washington to Florida. Outside of this track, in a belt varying in width from seventy miles at its western end to forty-five miles at its eastern, a partial eclipse will be visible

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