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POPULAR SCIENCE REVIEW. 
well-marked a feature disposed finally of the terrestrial theory. Dr. Balfour 
Stewart, in a letter read at the same meeting, pointed to the decisive nature 
of the evidence afforded by the darkness of the moon in Mr. Brothers’ pho- 
tograph, mentioning, also (as Mr. Proctor had already done in a paper read 
a year before *), that on a priori grounds the atmospheric explanation of 
the radiations was untenable, since the proportion which atmospheric glare 
due to the inner corona would bear to the corona itself would be the same, 
or nearly so, as the proportion which the atmospheric glare in full sunlight 
bears to that sunlight — i.e. would be exceedingly small. In fact, at this 
meeting of the Royal Astronomical Society one piece of evidence after 
another was brought to bear against the unfortunate 11 atmospheric glare ” 
theory, in whose favour not one of those present seemed ready to venture a 
word. 
The Results of the Eclipse Expeditions . — Freed thus from the incubus of 
an erroneous theory which had too long been suffered to attract attention, 
let us consider the real results of the late expeditions. One can hardly 
speak of the proof that the corona has a real existence, and is a real solar 
appendage, as a result of the late expeditions, because it had, in effect, been 
demonstrated much earlier ; though undoubtedly the acquisition of evidence 
easily interpretable and generally convincing must be regarded as a gain. 
But the student of science has a right to inquire what fresh knowledge has 
been acquired. It appears to us that by far the most important result of the 
expeditions is to be found in the evidence which the photographs give as to 
the structure of the corona. We have seen that Lieut. Brown bad noticed 
that the inner and brighter part of the corona is much shallower where the 
great gap appears, and that Professor Watson’s drawings confirm this. But 
the evidence of the American photographs and Mr. Brothers’s is decisive on 
the point. The correspondence between the outer radiations and the inner 
brighter portion of the corona is unmistakable. This is a phenomenon 
worthy of the most careful . study. It can only be explained — nobis judici- 
bus — as due to the action of solar forces exerted radially; but whether 
those forces be eruptive, or simply repulsive, is not so clear. The action of 
eruptive forces sufficing to account for the observed extension of the corona 
may seem at first to involve an incredible degree of activity beneath the 
solar photosphere ; but when it is mentioned that a velocity only three times 
as great as that with which the hydrogen of the prominences is observed to 
be flung out (after passing through the denser lower regions of the solar 
air) would suffice to project matter as far as our own earth, while a very 
* He thus wrote (“ Monthly Notices ” for March 1870) : u We know bow 
small a relation ordinary atmospheric glare bears to direct sunlight, and the 
glare due to the prominences and chromosphere ” (an objectionable word — 
he should have written sierra ) “ would bear a similar relation to the direct 
light from those sources.” He added that the light from this source “ would 
extend over the moon’s disc, since it would illuminate the air between the 
observer and the moon’s body.” The fact that such light was recognised by 
the spectroscopists during the late eclipse — the bright line coronal spectrum 
being actually discernible when the spectroscope was directed to the middle 
of the moon’s disc, shows how, by careful reasoning, the results of observa- 
tion may be anticipated. 
