e, for his musical pupils were getting
impatient. They had to get the better of their impatience, however, for
the King ultimately appointed him astronomer or rather telescope-maker
to himself, and so Caroline and the whole household were sent for, and
established in a small house at Datchet.

From being a star-gazing musician, Herschel thus became a practical
astronomer. Henceforth he lived in his observatory; only on wet and
moonlight nights could he be torn away from it. The day-time he devoted
to making his long-contemplated 20-foot telescope.

Not yet, however, were all their difficulties removed. The house at
Datchet was a tumble-down barn of a place, chosen rather as a workshop
and observatory than as a dwelling-house. And the salary allowed him by
George III. was scarcely a princely one. It was, as a matter of fact,
L200 a year. The idea was that he would earn his living by making
telescopes, and so indeed he did. He made altogether some hundreds.
Among others, four for the King. But this eternal making of telescopes
for other people to use or play with was a weariness to the flesh. What
he wanted was to observe, observe, observe.

Sir William Watson, an old friend of his, and of some influence at
Court, expressed his mind pretty plainly concerning Herschel's position;
and as soon as the King got to understand that there was anything the
matter, he immediately offered L2,000 for a gigantic telescope to be
made for Herschel's own use. Nothing better did he want in life. The
whole army of carpenters and craftsmen resident in Datchet were pressed
into the service. Furnaces for the speculum metal were built, stands
erected, and the 40-foot telescope fairly begun. It cost L4,000 before
it was finished, but the King paid the whole.

[Illustration: FIG. 83.--Herschel's 40-foot telescope.]

With it he discovered two more satellites to Saturn (five hitherto had
been known), and two moons to his own planet Uranus. These two are now
known as Oberon and Titania. They were not seen again till some forty
years after, when his son, Sir John Herschel, reobserved them. And in
1847, Mr. Lassell, at his house, "Starfield," near Liverpool, discovered
two more, called Ariel and Umbriel, making the number four, as now
known. Mr. Lassell also discovered, with a telescope of his own making,
an eighth satellite of Saturn--Hyperion--and a satellite to Neptune.

A letter from a foreign astronomer about this period describes Herschel