Page:Popular Science Monthly Volume 14.djvu/679

Rh surrounding the sun, proved the long rays extending much farther from the sun to be non-solar phenomena. "The non-solar origin of the radial structure," said Mr. Lockyer as late as July 20th last, "was conclusively established" during the eclipse of December, 1871.

To say the truth, there is no possible way of interpreting the lon grays as phenomena of our own atmosphere or of matter (gaseous, meteoric, or dust-like) on the hither side of the moon. The idea is one which mathematicians may casually have thrown out. Indeed, Mädler and Airy, after the eclipse of 1860, advanced the hypothesis that the long rays belong to matter between us and the moon, while Sir John Herschel adopted in his "Familiar Lectures" the notion that these rays belong to matter at a great height in our own atmosphere. But it would be to misrepresent these eminent astronomers to assert that they ever maintained these views. The available evidence, analyzed as any one of these mathematicians could have analyzed it, had he seen fit, would have shown convincingly that the rays must come from matter lying far beyond the moon. Sir John Herschel admitted this in a letter addressed to the present writer. Whether Airy or Mädler ever examined the evidence closely we do not know. If they did they doubtless were led to the same result as Sir J. Herschel. The matter may be put in this way: Since these long rays extend from the black disk of the moon during mid totality, they occupy then a part of the sky where no sun-illuminated air lies at such a time; therefore they cannot belong to our air; but if there were some very tenuous matter, aerial or dust-like, extending as far as the moon's orbit, the whole region of the sky athwart which these rays extend would contain matter of this sort under full solar illumination; no rays then would be seen, but a nearly uniform glare, which should become brighter and brighter as the distance from the sun's place increased. If we add to this that at midnight the whole of the sky, except a round spot some four or five times the diameter of the moon, would be occupied by this cis-lunar matter under direct solar illumination, instead of that illumination from behind which such matter would receive during total eclipse, we see that the darkness of our midnight sky speaks as decisively against this theory as does the brightness of the long rays seen during total eclipse.

Notwithstanding the overwhelming evidence available to show that these rays lie far beyond the moon, Professor Abbe had adopted the opinion that the rays belong to the earth's atmosphere, or else are mere optical illusions. "I had hitherto firmly believed them," he says, "to be either in the earth's atmosphere or in the observer's eyes. . . . Such rays," he adds, "were seen by members of my eclipse party at Sioux Falls City, Dakota, August, 1869; but at that time and ever since I have doubted their existence." It is manifest that he did not begin his observations with the preconceived idea that the rays belong to matter far more distant than the moon, but with a strong opinion, if not a strong prejudice, the other way.