of a globe-shaped aggregation of stars,
in which the individuals are set at fairly regular distances from each
other; the whole being closely encircled by a belt of densely packed
stars. It must, however, be allowed that the gradual increase in the
number of stars towards the Milky Way appears a strong argument in
favour of the grindstone theory; yet the belt theory, as above detailed,
seems to meet with more acceptance.

There is, in fact, one marked circumstance which is remarkably difficult
of explanation by means of the grindstone theory. This is the existence
of vacant spaces--holes, so to speak, in the groundwork of the Milky
Way. For instance, there is a cleft running for a good distance along
its length, and there is also a starless gap in its southern portion. It
seems rather improbable that such a great number of stars could have
arranged themselves so conveniently, as to give us a clear view right
out into empty space through such a system in its greatest thickness;
as if, in fact, holes had been bored, and clefts made, from the boundary
of the disc clean up to where our solar system lies. Sir John Herschel
long ago drew attention to this point very forcibly. It is plain that
such vacant spaces can, on the other hand, be more simply explained as
mere holes in a belt; and the best authorities maintain that the
appearance of the Milky Way confirms a view of this kind.

Whichever theory be indeed the correct one, it appears at any rate that
the stars do not stretch out in every direction to an infinite distance;
but that _the stellar system is of limited extent_, and has in fact a
boundary.

In the first place, Science has no grounds for supposing that light is
in any way absorbed or destroyed merely by its passage through the
"ether," that imponderable medium which is believed to transmit the
luminous radiations through space. This of course is tantamount to
saying that all the direct light from all the stars should reach us,
excepting that little which is absorbed in its passage through our own
atmosphere. If stars, and stars, and stars existed in every direction
outwards without end, it can be proved mathematically that in such
circumstances there could not remain the tiniest space in the sky
without a star to fill it, and that therefore the heavens would always
blaze with light, and the night would be as bright as the noonday.[36]
How very far indeed this is from being the case, may be gathered from an
es