LABOURS RELATIVE TO THE SOLAR SYSTEM. 295 
On the 28th of August, 1789, the great forty-foot 
telescope revealed to Herschel a satellite still nearer to 
the ring than the other five already observed. Accord- 
ing to the principles of the nomenclature previously 
adopted, the small body of the 28th August ought to 
have been called the first satellite of Saturn, the num- 
bers indicating the places of the other five would then 
have been each increased by a unity. But the fear of 
introducing confusion into science by these continual 
changes of denomination, induced a preference for calling 
the new satellite the sixth. 
Thanks to the prodigious powers of the forty-foot 
telescope, a last satellite, the seventh, showed itself on 
the 17th of September, 1789, between the sixth and the 
ring. ’ 
This seventh satellite is extremely faint. Herschel, 
however, succeeding in seeing it whenever circumstances 
were very favourable, even by the aid of the twenty- 
foot telescope. 
The discovery of the planet Uranus, the detection of 
its satellites, will always occupy one of the highest places 
among those by which modern astronomy is honoured. 
On the 13th of March, 1781, between ten and eleven 
o'clock at night, Herschel was examining the small stars 
near H Geminorum with a seven-foot telescope, bearing 
a magnifying power of 227 times. One of these stars 
seemed to him to have an unusual diameter. The cele- 
brated astronomer, therefore, thought it was a comet. It 
was under this denomination that it was then discussed 
at the Royal Society of London. But the researches of 
Herschel and of Laplace showed later that the orbit of 
the new body was nearly circular, and Uranus was ele- 
vated to the rank of a planet. 
