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wise. When Uranus is near either of these points, we, from the earth, see the satellites moving as if swinging up and down in a north and south direction on each side of the planet, like the bob of a pendulum. Then, as the planet moves on, the apparent orbits slowly open out. At the end of twenty years we see them perpendicularly. They then seem to us almost circular, but appear to close up again year after year as the planet moves on its course. The orbits were last seen edgewise in 1882, and will be again so seen about 1924. For several years to come the orbits are seen from a nearly perpendicular standpoint, which is the most favourable condition for observing the satellites.

It is quite possible that continued observations of these bodies will yet enable the astronomer to reach some conclusion to the hitherto unsolved problem of the rotation of Uranus on its axis. In the cases of Mars, Jupiter, and Saturn, the satellites revolve very nearly in the plane of the equators of the several planets to which they belong. If this is true of Uranus, it would follow that the equator of the planet was nearly perpendicular to its orbit, and that its north pole, at two opposite points in its orbit, would point almost exactly to the sun. Such being the case, the seasons would be vastly more marked than they are on our earth. Only on or near the equator of Uranus would a denizen of the planet see the sun every day. If he lived in middle latitudes there would be a period equal in length to five or ten of our years during which the sun would never reach his horizon. Then, moving rapidly upwards, it would rise and set, giving him day and night,