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that, on June 5th, 1872, the two planets might have been seenat an apparent distance only equal to 1^ times the diameter ofJupiter , had not daylight prevented the observation. But, at9 p.m., Jupiter and its four satellites, together with Uranus ,were beautifully grouped in the field of view of the telescope;Uranus being situated almost exactly above the 3rd or largestsatellite. The two were apparently of the same size, but theplanet was rather more brilliant in its light. It thereforefollows that the light of Uranus (at that time) slightly exceededthat of a 6th magnitude star, and that it is, as observation hasoften proved to be the case, under such circumstances justperceptible by the naked eye.
The Planet Neptune.
We have already more than once mentioned the planet Neptune as the most remote from the Sun of all those withwhich we are acquainted. We have spoken of its orbit aslying very far beyond that of Uranus ; but we have not as yetreferred to the very remarkable character of the investigationsby which it was discovered in the year 1846.
That discovery, which we now proceed to explain, is un-doubtedly the greatest modern triumph of the mathematicsof astronomy; a triumph which makes us feel how much moreappropriate the word “now" would be, if substituted for thetwice recurring “ nor" in the lines of Prior: —
“ Each planet shining in his proper sphere,
Doth with just speed his radiant voyage steer ;
And in his passage through the liquid space,
Nor hastens, nor 'retards, his neighbour’s race.”
Most of our readers may already be aware, that this lastaddition to the known members of the Sun’s family wasdetected in its far distant path by no mere chance or accident.There was nothing unexpected in the first observation of it, asin the case of Uranus . On the contrary, two great mathema-ticians who, in common with the rest of the scientific world,had good reasons for believing that such a planet must exist,calculated, by long and arduous processes, in what directionto point the telescope by means of which it should be seen.