The latest astronomical paradox published is perhaps still more startling. It relates to the planet Venus, and is intended to explain the appearance presented by this planet when crossing the sun's face, or, technically, when in transit. At this time she is surrounded by a ring of light, which appears somewhat brighter than the disc of the sun itself. Before fully entering on the sun's face, also, the part of Venus's globe as yet outside the sun's disc is seen to be girt round by a ring of exceedingly bright light--so bright, indeed, that it has left its record in photographs where the exposure was only for the small fraction of a second allowable in the case of so intensely brilliant a body as the sun. Astronomers have not found it difficult to explain either peculiarity. It has been proved clearly in other ways that Venus has an atmosphere like our own, but probably denser. As the sun is raised into view above the horizon (after he has really passed below the horizon plane) by the bending power of our air upon his rays, so the bending power of Venus's air brings the sun into our view round the dark body of the planet. But the new paradox advances a much bolder theory. Instead of an atmosphere such as ours, Venus has a glass envelope; and instead of a surface of earth and water, in some cases covered with clouds, Venus has a surface shining with metallic lustre.[53] The author of this theory, Mr. Jos. Brett, startled astronomers by announcing, a few years ago, that with an ordinary telescope he could see the light of the sun's corona without the aid of an eclipse, though astronomers had observed that the delicate light of the corona fades out of view with the first returning rays of the sun after total eclipse. The latest paradoxist, misled by the incorrect term 'centrifugal force,' proposes to 'modify, if not banish,' the old-fashioned astronomy. What is called centrifugal force is in truth only inertia. In the familiar instance of a body whirled round by a string, the breaking of the string no more implies that an active force has pulled away the body, than the breaking of a rope by which a weight is pulled implies that the weight has exerted an active resistance. Of course, here again the text-books are chiefly in fault. Such are a few among the paradoxes of various orders by which astronomers, like the students of other sciences, have been from time to time amused. It is not altogether, as it may seem at first sight, 'a sin against the twenty-four hours' to consider such matters; for much may be learned not only from the study of the right road in science, but from observing where and how men may go astray. I know, indeed, few more useful exercises for the learner than to examine a few paradoxes, when leisure serves, and to consider how, if left to his own guidance, he would confute them. XI. _ON SOME ASTRONOMICAL MYTHS._