Uranus was discovered to be a planet by Sir William Herschel in 1781, and in 1787 he discovered two satellites, whose periods were satisfactorily determined by his subsequent observations. In 1797 he announced the discovery of four additional satellites, viz., one within the orbits of both the former two; one intermediate between the two; and two exterior to both of them, but the periods of these satellites he acknowledged to be very uncertain. In his last paper on this subject, communicated to the Eoyal Society in 1815, he says, “that there are additional satellites, besides the two principal larger ones, I can have no doubt; but to determine their number and situation, will probably require an increase of illuminating power in our telescopes.”

In 1834, Sir John Herschel published a paper containing a thorough discussion of his father's observations, together with his own, upon the two satellites first discovered; and he adds, “of other satellites than these two, I have no evidence.”

In the year 1838, Dr. Lamont, of Munich, published a few observations of the two brighter satellites of Uranus, and states that he had seen only one additional satellite, and that but in a single instance. This satellite he considered to be the most remote of the six enumerated by Herschel.

With the exception, therefore, of the solitary observation of Dr. Lamont, the only evidence we have had (until recently) of the existence of more than two satellites of Uranus was derived from the observations of Sir William Herschel; and he would not pronounce a decided opinion as to their number or their periods of revolution.