Page:Popular Science Monthly Volume 16.djvu/131

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ROM Professor Langley's address at the Saratoga Scientific Association, on the recent progress of solar physics, which is herewith printed, we get a vivid idea of the rapidity with which knowledge upon this subject has advanced within a very few years. We have found out more about the most conspicuous and familiar object in the universe in the last twenty years than all that was known before put together. A late writer in the London "Times" draws attention to the views now taken in regard to the solar surroundings. He considers that recent observations have tended toward marked agreement in the opinions entertained respecting coronal phenomena, and their relation to the zodiacal light. In presenting the results of observations on the eclipse of 1878 those are first taken which give the luminous effects displayed nearest the sun. Mr. Lockyer's drawing represents the black body of the moon as surrounded by a narrow ring of light, the inner corona. Outside this ring are three projections nearly in the ecliptic, and therefore coinciding with the axis of the zodiacal light. The longest of these projections extended to about one and a quarter of the sun's diameter, or not far from one million miles. General Myer described the corona as showing five radial lines of a golden color, beyond which in the direction of the ecliptic were prolonged bright silver rays. General Myer had observed effects so similar in the eclipse of 1869 as to make probable the inference that the objects extending far away from the sun are not subject to change like the prominences. Mr. Alfred C. Thomas also observed streamers of light extending for about one and a half time the diameter of the moon, and also in the plane of the ecliptic. Professor Cleveland Abbe saw the streamers which other observers had compared to a wind-vane, but he traced them to a much greater distance than they had done. The point of the vane as he saw it reached away from the sun to fully six diameters, or more than five million miles. The breadth of the vane, where it crosses the sun, is almost exactly equal to the solar diameter. On the other side of the sun the double streamer forming the tail of the vane did not extend more than three million miles. He also saw other luminous streaks at right angles with these, but of less breadth and length. Professor Langley saw the coronal light extending farther than the long rays observed by Professor Abbe. He traced it to a distance of twelve diameters of the sun on one side and three on the other. Its extension was in the direction of the ecliptic and the light resembled the zodiacal. At its extreme distance from the sun it was a faint and softly graduated luminosity, and not the separate rays discerned at about half the distance. Professor Newcomb saw a similar luminosity, and traced it to the same distance from the sun that had been assigned by Professor Langley. The results are thus summed up by the "Times" writer:

From a comparison of all the observations the following important conclusions seem established beyond all possibility of doubt or question: Outside the solar sierra, averaging some 6,000 or 7,000 miles in height, comes the prominence region, extending about 100,000 miles from the sun's surface. Outside this comes the inner corona, shining in part with its own light, sometimes coming chiefly from multitudes of solid or liquid bodies in a state of incandescence, sometimes chiefly from glowing vaporous matter. This region