mountains must be several hundred miles away, for the reason that

they are almost entirely above the horizon. This apparent

flatness and wide range of vision is of course the result of

Jupiter's vast size. With sufficiently keen sight, or aided by a

good glass, there is no reason why one should not see at least

five hundred miles, with but a slight elevation."

"It is surprising," said Ayrault, "that in what is evidently

Jupiter's Carboniferous period the atmosphere should be so clear.