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 times every night! Phœbe seems to be possessed with a streak of contrariness for she moves in her orbit around Saturn in the opposite direction from all of the other moons.

Japetus, the second largest satellite, has the interesting peculiarity of appearing three or four times as bright when on the western side of Saturn as when on the eastern side of it. This is explained by the supposition that one of its sides has a greater reflecting power than the other and, like our moon, always has the same side toward its planet. We would, therefore, see one side of it when east of Saturn and the other side of it when west of it.

Themis, the tenth moon, was first recognized by W. H. Pickering in 1905 but it is only recently that its discovery was fully confirmed. Professor Pickering also discovered the ninth moon of Saturn.