Here, too, we find traces
of Herschel's labours. Not only has he enlarged our knowledge of its
equatorial compression, of its physical constitution, and of the
rotation of its luminous belt or ring, but he added two to the number
of its satellites. Five only of these were known at the close of the
seventeenth century; of which Cussiric discovered four, and Huygens one.
It was universally believed that the subject was exhausted.
But, on the 28th of August 1780, Herschel's colossal tube revealed to
his delighted gaze a satellite nearer to the Saturnian ring than those
previously observed. And a few days later, on the 17th of September, a
seventh and last satellite crossed his field of vision. It was situated
between the former and the ring; that is, it is the nearest to it of the
seven.
But the most remarkable of Herschel's achievements was the discovery of
the planet Uranus, and the detection of its satellites.
On the 13th of March 1781, between ten and eleven o'clock at night, the
great astronomer was engaged in examining the small stars near H in the
constellation Gemini, with a seven-foot telescope, bearing a magnifying
power of two hundred and twenty-seven times.
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