ular kind of orbit which
each star completes? Is the orbit that of an ellipse, or a circle, or a
parabola?

That it must have some kind of orbit is obvious from the proper motions
exhibited by the several stars. We have already learned from Arts. 107
and 108 that the sun possesses an orbit, which orbit fulfils the first
and second of Kepler's Laws.

If therefore the sun, as representing all stars, is subject to Kepler's
Laws, then, according to our Second Rule of Philosophy by which we base
our hypotheses on our experience, we are compelled to come to the
conclusion that every star which possesses any motion at all through
space must also be subject to Kepler's Laws, and therefore must each
possess a controlling centre around which they severally revolve. Kepler
himself was of the opinion that the stars were subject to the laws which
go by his name, and this view of the subject was also accepted by Sir
William Herschel.

Thus from philosophical considerations we affirm that each star, while it
is itself the centre of a starry system, is also dependent upon and
associated with some other body, to which it is held bound by the
electro-magnetic Aether, and around which it is made to revolve by the
circulating electro-magnetic currents associated with that central body.
So that by philosophical reasoning we are led to view the whole of the
innumerable stars that flood interstellar space, not as so many individual
and isolated units, that have no relation to each other, but rather as
parts of one great system, which in its entirety may form in its ultimate
unity one harmonious whole, a universe.

As we come to consider star clusters and nebulae, we shall see how this
idea of unity seems to be manifested throughout all celestial phenomena.

ART. 119. _Aether and Nebulae._--In addition to the host of stars that
flood the infinite space, there are other celestial bodies that meet the
gaze of the astronomer as the telescope is turned upon the heavens.

These bodies, which are glowing masses of gaseous matter, are termed
Nebulae. The word Nebulae signifies a cloud, but they are not clouds in
the same sense as we apply that term to masses of vapour that exist in
our own atmosphere. Sir Wm. Herschel did more towards the discovery of
nebulae than perhaps any other astronomer, either before his time or
since. His labours in the direction were completed and enlarged by his
son, Sir John Herschel, who surveyed the Southern heav