THE SUN’S CORONA. 
385 
progressed, she would move across its interior, until she finally 
reached its other edge, at which instant the totality would 
end.” Dr. Curtis remarks, that “ the notion that the corona 
may he the luminosity of our own sunlit atmosphere beyond 
the belt of totality is also both theoretically impossible and 
practically proven false by the testimony of the photographs. 
As to the theoretical considerations, it is sufficient to point out 
that with the diameter of the moon’s shadow upon the earth 
two or three times as great as the vertical extent of our own 
atmosphere, it is geometrically impossible for an observer near 
the centre of that shadow to see any portions of our atmo- 
sphere which lie beyond the cone of darkness — which portions 
alone, of course, could under the circumstances be illuminated 
— in apparent contiguity with the moon’s limb.” 
The evidence against the theory derived from this simple 
consideration, — first pointed out by Mr. Baxendell, I believe, 
— is so simple and so convincing, that it seems useless to 
consider further arguments. 
But then there is another mode in which the theory has 
recently been defended. It is pointed out that it is a mistake 
altogether to imagine that the advocates of the atmospheric- 
glare theory had overlooked considerations so simple and so 
obvious. They had not imagined, it would seem, that the 
solar rays pass directly into the moon’s shadow-cone, but that 
these rays are introduced into the shadow-cone by means of a 
possible action exerted near the moon’s limb.* The theory is 
thus made to resemble La Hire’s, described in these words by 
Prof. Grant : — u La Hire suggested that the corona might be 
produced by the reflection of the solar rays from the inequali- 
* Mr. Lockyer remarks, that both Dr. Gould and M. Faye have expressed 
such an opinion. It is possible that M. Faye may ; but I may venture to 
say, very confidently, that Dr. Gould is not an advocate of the atmospheric- 
glare theory of the corona, and has advanced no line of reasoning in its sup- 
port. lie has pointed to certain peculiarities observed during the American 
eclipse (respecting which, however, Dr. Curtis remarks that all other 
observers are at issue with him) ; and he remarks respecting these, that they 
seem to point to parts of the corona as belonging to our atmosphere. But 
he told me distinctly, after the last meeting of the Royal Astronomical 
Society, at which he had been present as a visitor, that he had no theory of 
the corona, and was content with stating what he had seen. 
What Dr. Gould has remarked about the moon’s possible action is, that 
the apparent encroachment of the prominence-bases on the lunar disc may 
be due to specular reflection of the moon’s surface. This view has no 
bearing whatever on the subject of the corona; but if it had, then Dr. 
Curtis’s proof that the encroachment referred to is a purely photographic 
phenomenon — a view confirmed by Dr. Mayer — would serve to dispose of any 
reasoning founded on the observed fact. 
VOL. IX. — NO. XXXVII. C C 
