earnestly directed since telescopes have been so much enlarged.
Photography also has enabled a vast amount of work to be covered in a
comparatively short period, and the spectroscope has given them the
means, not only of studying the chemistry of the heavens, but also of
detecting any motion in the line of sight from less than a mile a
second and upwards in any star, however distant, provided it be bright
enough.

[Illustration: SIR WILLIAM HERSCHEL, F.R.S.--1738-1822. Painted by
Lemuel F. Abbott; National Portrait Gallery, Room XX.]

In the field of telescopic discovery beyond our solar system there is
no one who has enlarged our knowledge so much as Sir William Herschel,
to whom we owe the greatest discovery in dynamical astronomy among the
stars--viz., that the law of gravitation extends to the most distant
stars, and that many of them describe elliptic orbits about each
other. W. Herschel was born at Hanover in 1738, came to England in
1758 as a trained musician, and died in 1822. He studied science when
he could, and hired a telescope, until he learnt to make his own
specula and telescopes. He made 430 parabolic specula in twenty-one
years. He discovered 2,500 nebulae and 806 double stars, counted the
stars in 3,400 guage-fields, and compared the principal stars
photometrically.

Some of the things for which he is best known were results of those
accidents that happen only to the indefatigable enthusiast. Such was
the discovery of Uranus, which led to funds being provided for
constructing his 40-feet telescope, after which, in 1786, he settled
at Slough. In the same way, while trying to detect the annual parallax
of the stars, he failed in that quest, but discovered binary systems