Page:Astronomy for Everybody.djvu/171

power completed. Then, at the first opportunity, he found that he could see the prominences without an eclipse!

At that time communication with India was by mail, so that for the news of Mr. Janssen's discovery astronomers had to wait until a ship arrived. By a singular coincidence his report and Mr. Lockyer's communication announcing his own discovery reached the French Academy of Sciences at the same meeting. This eminent body, with pardonable enthusiasm, caused a medal to be struck in commemoration of the new method of research, in which the profiles of Lockyer and Janssen appeared together as co-discoverers. Since that time the prominences are regularly mapped out from day to day by spectroscopic observers in various parts of the world.

The greatest beauty of a total eclipse is due to the sun's corona. The exact nature of this appendage is still in doubt. Indeed, until photography was called to the aid of the astronomer its structure was unknown. It was described by observers simply as a soft light surrounding the sun; but when it is photographed and carefully examined it is found to be of a radial, hairy structure which the reader can easily see from the frontispiece of the book. It extends out farthest in the direction of the sun's equator and least at the poles. The rays which chance to be exactly at the poles go straight out from the sun. But those on each side are found to curve toward the equator, while farther from the equator they are lost in the more powerful effulgence going out from the region of the solar spots. Near the poles the