i88 3 .] 
The Velocity of Light . 509 
and what gives rigidity to a whirling liquid within a bounded 
space but centrifugality reflected, which is the outcome of 
centripetality, of plain matter ? Centrifugality cannot pro- 
duce an effeCt greater than its cause : a liquid at the limit 
of absolute rigidity by vortex motion would either break its 
boundaries or destroy its own motion, collapse ; and centri- 
petality, and consequent polarity, would be re-established 
by increase of density of the one part, and creation of a 
vacuum of the other, inside a bounded space. 
Can one not see that a gas, a liquid, a solid, anything 
having no interstices, — that is, no inner surfaces, no dispa- 
rities of inner motion, but filling all space with uniformity, 
— is nothing ? 
I ask the thoughtful amongst the professors of the infal- 
lible creed, with all its sectarianisms, Is there anything more 
difficult of conception and explanation in aCtion at a distance 
than in the existence of matter ? Any least volume taken 
as a sphere, not moving, as a nucleus, a point, surrounded 
by one or more concentric strata of least thickness, is abso- 
lutely contiguous matter when the difference of attraction 
from an interior to the next exterior stratum or surface is 
less than the difference in excess of size of the exterior over 
the interior surface, which may represent as well a decrease 
as an increase of attraction toward the centre of the whole 
space or volume ; but when equality is reached attraction 
towards this common centre simply increases with the size 
of the surrounding concentric surfaces, which then represent 
vacuum. There is no difference between matter and 
vacuum, but an addition of force with additional space, 
which may be as well a relative gain as loss of force in pro- 
portion to increasing surface of attracting volume, and an 
absolute subtraction of attracting force equal to the increase 
of the attracting surface. 
If matter was absolutely contiguous, without separating 
absolute vacuum, if there were no aCtion at a distance there 
could be no matter ; it had to crush itself out of existence 
to result in absolute rest which — for us finite beings and 
brains inconceivable like infinity — yet is ; vacuum furnishes 
the possibility of extending motion, which, together with 
attracting motion, is the existence of something. 
We know of light only because we have an organ con- 
structed to make us aware of it. Light appears only where 
there is matter thus moved that it enlightens our eye. 
Issuing from matter, radiating all round, light spreads in 
equal matter in equal manner, and in different matter in 
different manner with decreasing intensity, or is partly or 
wholly reflected by opposing matter. 
