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rOPULAH SCIENCE REVIEW. 
sition that the air at this height of 1,000 miles is capable of 
being illuminated by the solar rays in such sort as to seem 
bright to observers 1,000 miles below. Then the observer 
may be regarded as placed at the bottom of a circular well of 
shadow, 150 miles in diameter at the bottom, and about 170 
miles in diameter at the top, the walls of this imaginary well 
being visible to him as light. How large, then, would the 
black opening at the top — for such it must seem to him — 
actually appear ? A disc of 170 miles at a distance of 1,000 
miles subtends an angle of about 9J degrees ; and such, therefore, 
would be the size of the disc of darkness. But the moon, 
which would be at the centre of this black circle, subtends only 
about half a degree, so that for a breadth of more than 4^- 
degrees all round the eclipsed moon there would be a ring of 
darkness ; but this is precisely the region where we require to 
have light, if the corona is to be accounted for by the theory 
we are now upon. 
If it be asked how high the atmosphere must be in order 
that this ring of darkness may be reduced sufficiently to bring 
the light close to the moon, the answer is, that the atmosphere 
must reach right up to the moon’s immediate neighbourhood. 
Prof. Harkness and Dr. Curtis, in discussing the results of 
the American eclipse, employ the argument here insisted upon. 
u The moon’s shadow,” says the former, “ at the point where it 
enters the earth’s atmosphere, usually has a diameter of more 
than 100 miles; and if it were possible for an observer 
placed within the shadow to see the illumination of the atmo- 
sphere outside of it, the appearance presented would be that of 
a halo having an inferior diameter much greater than the size 
of the moon. At the commencement of the totality the moon 
would be within and tangent to this halo ; and as the eclipse 
not omitting to notice some objection which everyone else has recognised. 
Mr. Williams here fails wholly to see that the balancing of forces is not 
equivalent to their annulment. A body resting on the ground is subject to 
the balanced forces of its own weight and the earth’s resistance ; yet it is 
not, therefore, free to be “ brushed oil” by the lightest zephyr; nay, it may 
be able to resist the impulse of a hurricane. And the same is true (on the 
hypothesis attacked by Mr. Williams) respecting the outermost atoms of 
the earth’s atmosphere. The surrounding ether is as powerless to remove 
them, as to carry the earth bodily away from the sun. 
I am not here advocating the atomic theory, though I confess all other 
theories of tie ultimate constitution of the elements seem inconceivable; I 
am simply endeavouring to show that this particular objection is founded on a 
fallacy. The objection founded on the behaviour of gases under a process of 
larification, down to the supposed occurrence of a real vacuum, will be worth 
considering when it has been proved that a real vacuum has been produced. 
The cessation of the transmission of the electric discharge proves nothing. 
