gives his
observations and computations in full. He says that of the existence of
additional satellites he has no doubt. Of these four, three were
exterior to the most distant satellite _Oberon_, the other was
"interior" to _Titania_.

It was not until 1834 that even _Oberon_ and _Titania_ were again
observed (by Sir JOHN HERSCHEL) with a telescope of twenty feet, similar
to that which had discovered them, and not until 1847 was the true state
of this system known, when Mr. LASSELL discovered _Ariel_ and _Umbriel_,
two satellites interior to _Titania_, neither of which was HERSCHEL'S
"interior" satellite. In 1848 and later years Mr. LASSELL, by the aid of
telescopes constructed by himself, fully settled the fact that only
four satellites of this planet existed. In 1874 I examined the
observations of HERSCHEL on his supposed "interior" satellite, thinking
that it might be possible that among the very few glimpses of it which
he recorded, some might have belonged to _Ariel_ and some to _Umbriel_,
and that by combining rare and almost accidental observations of two
satellites which really existed, he had come to announce the existence
of an "interior" satellite which had no existence in fact. Such I
believe to be the case. In 1801, April 17, HERSCHEL describes an
interior satellite in the position angle 189 deg., distant 18" from
the planet. At that instant _Umbriel_, one of Mr. LASSELL'S satellites,
was in the position 191 deg., and distant 21" from _Uranus_, in the
most favorable position for seeing it. The observation of 1794, March
27, _may_ belong to _Ariel_. At the best the investigation is of passing
interest only, and has nothing to do with the question of the discovery
of the satellites. HERSCHEL discovered the two brighter ones, and it
was only sixty years later that they were properly re-observed by Mr.
LASSELL, who has the great honor of having added as many more, and who
first settled the vexed question of satellites _exterior_ to _Oberon_,
and this with a reflecting telescope made by himself, which is
unequalled by any other of its dimensions.

_Researches on the Nature of the Sun._

In the introduction to his paper on the _Nature and Construction of the
Sun and Fixed Stars_ (1795), HERSCHEL recounts what was known of the
nature of the sun at that time. NEWTON had shown that it was the centre
of the system; GALILEO and his successors had determined its rotation,
the place of its equat