inguished from white in their
catalogues.

Herschel also endeavoured to introduce numbers in the classification of
stars as to magnitude; he has endeavoured, by means of numbers, to show
the comparative intensity of a star of first magnitude, with one of
second, or one of third magnitude, &c.

In one of the earliest of Herschel's memoirs, we find, that the apparent
sidereal diameters are proved to be for the greater part factitious,
even when the best made telescopes are used. Diameters estimated by
seconds, that is to say, reduced according to the magnifying power,
diminish as the magnifying power is increased. These results are of the
greatest importance.

In the course of his investigation of sidereal parallax, though without
finding it, Herschel made an important discovery; that of the proper
motion of our system. To show distinctly the direction of the motion of
the solar system, not only was a displacement of the sidereal
perspective required, but profound mathematical knowledge, and a
peculiar tact. This peculiar tact Herschel possessed in an eminent
degree. Moreover, the result deduced from the very small number of
proper motions known at the beginning of 1783, has been found almost to
agree with that found recently by clever astronomers, by the application
of subtile analytical formulae, to a considerable number of exact
observations.

The proper motions of the stars have been known and proved for more than
a century, and already Fontenelle used to say in 1738, that the sun
probably also moved in a similar way. The idea of partly attributing the
displacement of the stars to a motion of the sun, had suggested itself
to Bradley and to Mayer. And Lambert especially had been very explicit
on the subject. Until then, however, there were only conjectures and
mere probabilities. Herschel passed those limits. He himself proved
that the sun positively moves; and that, in this respect also, that
immense and dazzling body must be ranged among the stars; that the
apparently inextricable irregularities of numerous sidereal proper
motions arise in great measure from the displacement of the solar
system; that, in short, the point of space towards which we are annually
advancing, is situated in the constellation of Hercules.

These are magnificent results. The discovery of the proper motion of our
system will always be accounted among Herschel's highest claims to
glory, even after the mention that my duty as historian ha