laws dependent
upon the velocity of light.

At one particular region of the heavens the effect of aberration has a
degree of simplicity which is not manifested anywhere else. This region
lies in the constellation Draco, at the pole of the ecliptic. At this
pole, or in its immediate neighbourhood, each star, in virtue of
aberration, describes a circle in the heavens. This circle is very
minute; it would take something like 2,000 of these circles together to
form an area equal to the area of the moon. Expressed in the usual
astronomical language, we should say that the diameter of this small
circle is about 40.9 seconds of arc. This is a quantity which, though
small to the unaided eye, is really of great relative magnitude in the
present state of telescopic research. It is not only large enough to be
perceived, but it can be measured, with an accuracy which actually does
not admit of a doubt, to the hundredth part of the whole. It is also
observed that each star describes its little circle in precisely the
same period of time; and that period is one year, or, in other words,
the time of the revolution of the earth around the sun. It is found that
for all stars in this region, be they large stars or small, single or
double, white or coloured, the circles appropriate to each have all the
same size, and are all described in the same time. Even from this alone
it would be manifest that the cause of the phenomenon cannot lie in the
star itself. This unanimity in stars of every magnitude and distance
requires some simpler explanation.

Further examination of stars in different regions sheds new light on the
subject. As we proceed from the pole of the ecliptic, we still find that
each star exhibits an annual movement of the same character as the stars
just considered. In one respect, however, there is a difference. The
apparent path of the star is no longer a circle; it has become an
ellipse. It is, however, soon perceived that the shape and the position
of this ellipse are governed by the simple law that the further the star
is from the pole of the ecliptic the greater is the eccentricity of the
ellipse. The apparent path of the stars at the same distance from the
pole have equal eccentricity, and of the axes of the ellipse the shorter
is always directed to the pole, the longer being, of course,
perpendicular to it. It is, however, found that no matter how great the
eccentricity may become, the major axis always retains its o