s, as a man and a politician he hardly
commands our respect, and in time-serving adjustability he is comparable
to the redoubtable Vicar of Bray. His scientific insight and genius
were however unquestionably of the very highest order, and his work has
been invaluable to astronomy.

I will give a short sketch of some of his investigations, so far as they
can be made intelligible without overmuch labour. He worked very much in
conjunction with Lagrange, a more solid though a less brilliant man, and
it is both impossible and unnecessary for us to attempt to apportion
respective shares of credit between these two scientific giants, the
greatest scientific men that France ever produced.

First comes a research into the libration of the moon. This was
discovered by Galileo in his old age at Arcetri, just before his
blindness. The moon, as every one knows, keeps the same face to the
earth as it revolves round it. In other words, it does not rotate with
reference to the earth, though it does rotate with respect to outside
bodies. Its libration consists in a sort of oscillation, whereby it
shows us now a little more on one side, now a little more on the other,
so that altogether we are cognizant of more than one-half of its
surface--in fact, altogether of about three-fifths. It is a simple and
unimportant matter, easily explained.

The motion of the moon may be analyzed into a rotation about its
own axis combined with a revolution about the earth. The speed of
the rotation is quite uniform, the speed of the revolution is not
quite uniform, because the orbit is not circular but elliptical,
and the moon has to travel faster in perigee than in apogee (in
accordance with Kepler's second law). The consequence of this is
that we see a little too far round the body of the moon, first on
one side, then on the other. Hence it _appears_ to oscillate
slightly, like a lop-sided fly-wheel whose revolutions have been
allowed to die away so that they end in oscillations of small
amplitude.[23] Its axis of rotation, too, is not precisely
perpendicular to its plane of revolution, and therefore we
sometimes see a few hundred miles beyond its north pole, sometimes
a similar amount beyond its south. Lastly, there is a sort of
parallax effect, owing to the fact that we see the rising moon from
one point of view, and the setting moon from a point 8,000 miles
dista