l us regarding the orbit
which any body moving in space assumes? Take, for example, our moon as
illustrating the movement of all satellites, and our earth as
illustrating all planetary motion.

What does observation teach us as to the orbits which these bodies
describe? If it teaches us anything at all, it teaches us that every
satellite and planet moves with varying velocity in a varying orbit
around some central body. So far as our observation goes, then, in
relation to planetary motion, or the motion of satellites, we learn that
every body which moves in space fulfils Kepler's First Law, and
describes an orbit round a central body, that body occupying one of the
foci.

Thus, wherever we get any body moving in space, if there be any truth in
philosophy which is based on experiment and observation, that body ought
also to move in similar elliptic orbits, and be subject to exactly
similar conditions governing those orbits. But we have learned that the
sun moves through space with a velocity of about five miles per second,
therefore it follows, philosophically, that the sun must also move
around some other central body, and the path of such movement is that of
an elliptic orbit, with the central body around which it moves occupying
one of the foci.

In other words, the sun obeys the first of Kepler's Laws, the same as
all the planets and satellites do. Suppose, for a moment, that it is
denied that the sun moves in an elliptic orbit! What path would it
pursue in place of that? Would the path be that of a straight line
towards the constellation of Hercules? Such an assumption would be
altogether unphilosophical, as it is contrary to all experience and
observation, and is therefore untenable.

Before such an assumption can be made, it must be proved that every
planet and satellite moves in a straight line, and not till that has
been done can it be assumed that the sun moves in a straight line, or
indeed in any other path than that stated in the first of Kepler's Laws.

This conclusion is in perfect harmony with the conclusion arrived at by
Herschel, for in his work on _Astronomy_, in Arts. 292, 295 and 297, he
points out that the sun's path is elliptic in form, and that Kepler also
showed the sun fulfilled the first of his laws, and described an orbit
which was in the shape of an ellipse. We have therefore philosophically
arrived at the conclusion that the sun moves in an elliptic orbit, and
to do so it must move roun