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POPULAR SCIENCE REVIEW. 
brilliantly than the matter on this side of the moon, and pre- 
senting also a far greater depth of illuminated matter, ought 
to give nearly all the light seen close by the moon — let us, I 
say, neglect this consideration, and deal only with the matter 
lying between the moon and earth. Then the sun’s rays, pass- 
ing the rough edge of the moon and falling on this matter, 
would certainly produce a radial appearance, resembling very 
closely the corona as pictured by eclipse-observers. There 
would be bright radial beams and intervening narrow spaces, 
precisely as in the picture by Mr. W. S. Gilman, jun., in 
Commodore Sands’ report of the American eclipse. But in 
order that these radial beams should extend as far as they have 
been actually seen during eclipses, the matter capable of being 
thus illuminated should extend (one may easily calculate) fully 
200,000 miles from the moon towards the earth. Now, assuming 
with Oudemann, that this matter is the exterior part of the 
Zodiacal Light, there is no reason why it should not extend as 
far as this towards the earth, or very much farther. But, then, 
as the corona has been seen as well in June and July as in 
December and January, that is, as well when the earth is a 
million and a half miles beyond her mean distance as when 
she is as much within that distance, we are utterly prevented 
from supposing that the limits of this zodiacal matter lie always 
somewhere between the moon and earth, separated as these 
bodies are by less than a quarter of a million of miles. In 
fact, to account for the visibility of the corona in all total 
eclipses, we must assume that when the earth is in perihelion, 
the zodiacal matter extends three millions of miles or so (at 
least) beyond the earth. This matter, thus extending beyond 
the earth, ought to be visible at night in a far more conspicuous 
manner than the corona during totality. For, according to the 
theory, those particles within the quarter of a million of miles 
separating us from the moon which are but obliquely illuminated, 
and whose brilliancy is marred by the strong light continuing 
during even the most considerable total eclipse, are yet so con- 
spicuously lighted up as to show the radial beams on a bright 
background. How much more conspicuous then should be the 
illumination seen towards the south at midnight, where (accord- 
ing to the theory) a space some three millions of miles deep, full 
of this matter, is illuminated directly — or as the full moon is — 
while the darkness of night and the black background of the 
sky help to render the phenomenon more conspicuous. The 
black shadow of the earth would indeed be thrown as a long 
black rift across this illuminated region of the heavens ; but 
we know how far it would reach, and what its shape would be. 
Even at the moon’s distance the true shadow would be but 
about three times the moon’s diameter in breadth, while at a 
