Page:Popular Science Monthly Volume 1.djvu/28

18 It was hoped—and the hope would appear to have been justified—that during the late eclipse these doubts would be finally removed. A few weeks must elapse even after the present paper appears, and five or six from the present time of writing, before the sun-painted pictures, which are to decide the question, can be in the hands of the judges. But, from the description which has already reached us, we can feel very little doubt as to the nature of the decision which will be arrived at.

A brief sketch of the progress of the inquiry into the subject of the solar corona will serve to exhibit the nature of the doubts which the recent expeditions to the Indian seas were intended to remove.

From very early ages it had been known that when the sun's disk is wholly concealed by the moon, a glory of light starts into view, rendering the scene less terrible, though scarcely less striking, than it would be were total darkness to prevail.

Now, gradually, it began to be recognized that this glory around the sun consisted of several distinct portions. In the first place, quite close to the moon's black body, a very narrow ring of light had been observed, so bright that many astronomers were led to believe that the sun was not in reality totally concealed, but that a ring of sunlight remained even at the moment of central eclipse. This excessively bright ring of light is not, however, always seen, if (as many accounts suggest) it is to be distinguished from the bright inner corona of which I shall presently have to speak. During the recent eclipses we have had no clear evidence respecting this brilliant but very narrow ring; and it is just possible that the accounts derived from earlier eclipses have been a little exaggerated.

Then, secondly, a red border is seen around portions of the black disk of the moon. This border has commonly a serrated edge, and has been called the sierra, from a well-known Spanish name for a range of hills. From what thus resembles a chain of rose-colored mountains, appear to spring certain red projections which have been called the solar prominences. Their general appearance during eclipse may be inferred from the description given by those who first observed them, in 1842, who compared the moon's disk surrounded by these glowing objects to a black brooch set round with garnets. But it is now known that such names as prominences and protuberances are not properly applicable to these red objects, and that the word sierra is equally inapplicable to the rim of colored light beneath the red projections. The prominences as well as the sierra (for, however unsuitable, the names continue in use) are in reality formed of glowing gas, hydrogen being their chief constituent element, but other elements being also present in a gaseous form. Only, the reader must not run away with the notion that these great red masses, some of which are more than a hundred thousand miles in height, are of the nature of our