e void?
Granting that, in any or every direction, there is a limit to the
universe, and that the space beyond is therefore void, what is the form
of the whole system and the distance of its boundaries? Preliminary in
some sort to these questions are the more approachable ones: Of what
sort of matter is the universe formed? and into what sort of bodies is
this matter collected?

To the ancients the celestial sphere was a reality, instead of a mere
effect of perspective, as we regard it. The stars were set on its
surface, or at least at no great distance within its crystalline mass.
Outside of it imagination placed the empyrean. When and how these
conceptions vanished from the mind of man, it would be as hard to say
as when and how Santa Claus gets transformed in the mind of the child.
They are not treated as realities by any astronomical writer from
Ptolemy down; yet, the impressions and forms of thought to which they
gave rise are well marked in Copernicus and faintly evident in Kepler.
The latter was perhaps the first to suggest that the sun might be one
of the stars; yet, from defective knowledge of the relative brightness
of the latter, he was led to the conclusion that their distances from
each other were less than the distance which separated them from the
sun. The latter he supposed to stand in the centre of a vast vacant
region within the system of stars.

For us the great collection of millions of stars which are made known
to us by the telescope, together with all the invisible bodies which
may be contained within the limits of the system, form the universe.
Here the term "universe" is perhaps objectionable because there may be
other systems than the one with which we are acquainted. The term
stellar system is, therefore, a better one by which to designate the
collection of stars in question.

It is remarkable that the first known propounder of that theory of the
form and arrangement of the system which has been most generally
accepted seems to have been a writer otherwise unknown in
science--Thomas Wright, of Durham, England. He is said to have
published a book on the theory of the universe, about 1750. It does not
appear that this work was of a very scientific character, and it was,
perhaps, too much in the nature of a speculation to excite notice in
scientific circles. One of the curious features of the history is that
it was Kant who first cited Wright's theory, pointed out its accordance
with the appea