Mercury will again be visible for a short time about the middle of the month a little after the sun has set, arriving on the 16th at his greatest eastern elongation, or apparent distance from the centre of the system, as seen from the earth in 20 deg. _Leo_; and in aphelio, or that point of his orbit most distant from the sun, on the 22nd; he becomes stationary on the 29th. There is only one visible eclipse of Jupiter's first satellite this month--on the 5th, at 10h. 21m. evening. The Georgium Sidus, or Herschel, comes to an opposition with the sun on the 19th, at 6h. 15m. evening; he is then nearest the earth, and consequently in the most favourable position for observation; he began retrograding on the 1st of May in 28 deg. 12m. of _Capricornus_; he rises on the 1st, at 9h. 11m. evening, culminating at 1h. 16m., and setting at 5h. 21m. morning, pursuing the course of the sun on the 17th of January; he moves only 13m. of a deg. in the course of the month, rising 2 h. earlier on the 31st. This planet, called also Uranus, was discovered by Herschel on the 13th of March, 1781. It is the most distant orb in our system yet known. From certain inequalities on the motion of Jupiter and Saturn, the existence of a planet of considerable size beyond the orbit of either had been before suspected; its apparent magnitude, as seen from the earth, is about 3-1/2 sec., or of the size of a star of the sixth magnitude, and as from its distance from the sun, it shines but with a pale light, it cannot often be distinguished with the naked eye. Its diameter is about 4-1/2 times that of the earth, and completes its revolution in something less than 83-1/2 years. The want of light in this planet, on account of its great distance from the sun, is supplied by six moons, which revolve round their primary in different periods. There is a remarkable peculiarity attached to their orbits, which are nearly perpendicular to the plane of the ecliptic, and they revolve in them in a direction contrary to the order of the signs. "Moore," in an old almanack, speaking on the difference of light and heat enjoyed by the inhabitants of _Saturn_, and the _earth_, says,-- "From hence how large, how strong the sun's bright ball, But seen from thence, how languid and how small, When the keen north with all its fury blows, Congeals the floods and forms the fleecy snows: 'Tis heat intense, to what can there be known, Warmer our poles than in its burning (!) zone; One moment's cold like their's would pierce the bone, Freeze the heart's blood, and turn us all to stone."