When the red spot began to lose distinctness a kind of veil seemed to be drawn over it, as if light clouds, floating at a superior elevation, had drifted across it.  At times it has been reduced in this manner to a faint oval ring, the rim remaining visible after the central part has faded from sight.

One of the most remarkable phenomena connected with the mysterious spot is a great bend, or scallop, in the southern edge of the south belt adjacent to the spot.  This looks as if it were produced by the spot, or by the same cause to which the spot owes its existence.  If the spot were an immense mountainous elevation, and the belt a current of liquid, or of clouds, flowing past its base, one would expect to see some such bend in the stream.  The visual evidence that the belt is driven, or forced, away from the neighborhood of the spot seems complete.  The appearance of repulsion between them is very striking, and even when the spot fades nearly to invisibility the curve remains equally distinct, so that in using a telescope too small to reveal the spot itself one may discover its location by observing the bow in the south belt.  The suggestion of a resemblance to the flowing of a stream past the foot of an elevated promontory, or mountain, is strengthened by the fact, which was observed early in the history of the spot, that markings involved in the south belt have a quicker rate of rotation about the planet’s axis than that of the red spot, so that such markings, first seen in the rear of the red spot, gradually overtake and pass it, and eventually leave it behind, as boats in a river drift past a rock lying in the midst of the current.

This leads us to another significant fact concerning the peculiar condition of Jupiter’s surface.  Not only does the south belt move perceptibly faster than the red spot, but, generally speaking, the various markings on the surface of the planet move at different rates according as they are nearer to or farther from the equator.  Between the equator and latitude 30 deg. or 40 deg. there is a difference of six minutes in the rotation period—­i.e., the equatorial parts turn round the axis so much faster than the parts north and south of them, that in one rotation they gain six minutes of time.  In other words, the clouds over Jupiter’s equator flow past those in the middle latitudes with a relative velocity of 270 miles per hour.  But there are no sharp lines of separation between the different velocities; on the contrary, the swiftness of rotation gradually diminishes from the equator toward the poles, as it manifestly could not do if the visible surface of Jupiter were solid.