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THE SATELLITES OF JUPITER .

one joining the centre of the Sun and the Satellite. Theformer meets it where the Satellite while in transit acrossthe disc will, if distinguishable, be seen projected upon it. Thelatter indicates where the shadow of the Satellite falls uponthe planet.

Orbit cf the

Fig . LXXVIIL—Phenomena of Jupiter’s Satellites. The transit of a Satellite, and ofa Satellite’s shadow.

Nor is it hard to perceive, by noticing the directions of thearrows in the diagram, that, in the position in which the Earth is drawn, the Satellite (seen at t) will precede the shadow(seen at s) in its transit. Such a position corresponds to atime, shortly after the Earth has passed such a point as o, inFig . LXXVII., from which Jupiter is seen in Opposition. And