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rOPULAR SCIENCE REVIEW. 
ties of the moon’s surface contiguous to the edge of her disc, 
combined with their subsequent passage through the terres- 
trial atmosphere.” Prof. Grant, after discussing De Lisle’s 
evidence against La Hire’s view, remarks, that clearly “ the 
hypothesis was untenable.” 
Let us, however, apply what has been already inferred 
respecting the moon’s shadow-cone. Eeplacing our observer 
at the bottom of the imagined well of shadow, we have now to 
consider the case of light making its way into this well through 
the deflection of the solar rays. But we have one certain fact 
about the region of shadow. The moon looks black during 
total eclipse, and therefore it is abundantly evident that lines 
taken from the eye of the observer to the edge of the moon’s 
limb include within them a cone which is not illuminated. 
Now we have seen that, taking only the case of undeflected 
rays, we should have a shadow 170 miles in 
width at the top and 150 at the bottom, while 
the , cross-section at the top would subtend 
about 9 j degrees, the moon only subtending 
about half a degree. Hence the cone of black- 
ness between the eye and the moon’s disc oc- 
cupies a position quite clear of the imagined 
walls of our shadow-well. The shadow-well, 
in fact, is shaped somewhat as abcd in the 
figure, while the shadow-cone extends from the 
eye of the observer at e upwards through the 
middle of the shadow-well, as shown by the 
black region ef. 
Now, before the theory we are dealing with 
can be accepted, it must be shown how the 
solar rays, whose direct course would keep them outside abcd, 
can be brought within abcd without trenching at all upon the 
black cone ef. It is obvious that this is wholly impossible. If 
we get the rays within abcd, they can only avoid ef by 
travelling parallel to its surface (it is to be remembered that 
they must come quite up to its surface if the corona is to be 
accounted for) ; and it would thus follow that the rays which 
pass the moon’s edge are deflected exactly to e. But obviously, 
though this might happen for a moment during some particular 
eclipse, it could not by any possibility happen in all eclipses 
and throughout their continuance, since there is absolutely 
no fixed relation whatever between the point e and the 
boundary abcd of the geometrical shadow-cone, e is simply 
the station where the observer places himself, and is not 
necessarily on the axis of the shadow-cone at any moment, 
and is necessarily away from the axis at all moments save 
one. 
