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 visible, in the following position (Fig. 41). The further satellite was distant from Jupiter 10′, the nearer 0′ 20″, and they were in the same straight line; but at the fourth hour the satellite nearest to Jupiter no longer appeared, and the other seemed so diminished that it could scarcely be kept in sight, although the atmosphere was quite clear, and the satellite was further from Jupiter than before, since its distance was now 12′.

Feb. 11: 1 h.—There were two satellites on the east, and one on the west (Fig. 42). The western satellite was at a distance of 4′ from Jupiter. The satellite on the east, nearest to the planet, was likewise 4′ from Jupiter; but the satellite further to the east was at a distance from this one of 8′; they were fairly clear to view, and in the same straight line; but at the third hour the fourth satellite was visible near to Jupiter on the east, less in magnitude than the rest, separated from Jupiter by a distance of 0′ 30″, and slightly to the north out of the straight line drawn through the rest (Fig. 43). They were all very bright and extremely distinct, but at 5 h. 30 m. the satellite on the east nearest to Jupiter had moved further away from the planet, and was occupying a position midway between the planet and the neighbouring satellite further to the