vely mobile, like our clouds in the
atmosphere, while observation of their motion does not give the exact
period of the rotation of Jupiter. Some only appear upon the agitated
disk to vanish very quickly; others subsist for a considerable period.

One has been observed for over a quarter of a century, and appears to be
almost immobile upon this colossal globe. This spot, which was red at
its first appearance, is now pale and ghostly. It is oval (_vide_ Fig.
45) and measures 42,000 kilometers (26,040 miles) in length by 15,000
kilometers (9,300 miles) in width. Hence it is about four times as long
as the diameter of our Earth; that is, relatively to the size of
Jupiter, as are the dimensions of Australia in proportion to our globe.
The discussion of a larger number of observations leads us to see in it
a sort of continent in the making, a scoria recently ejected from the
mobile and still liquid and heated surface of the giant Jupiter. The
patch, however, oscillates perceptibly, and appears to be a floating
island.

We must add that this vast world, like the Sun, _does not rotate all in
one period_. Eight different currents can be perceived upon its surface.
The most rapid is that of the equatorial zone, which accomplishes its
revolution in 9 hours, 50 minutes, 29 seconds. A point situated on the
equator is therefore carried forward at a speed of 12,500 meters (7
miles) per second, and it is this giddy velocity of Jupiter that has
produced the flattening of the poles. From the equator to the poles, the
swiftness of the currents diminishes irregularly, and the difference
amounts to about five minutes between the movement of the equatorial
stream, and that of the northern and southern currents. But what is more
curious still is that the velocity of one and the same stream is subject
to certain fluctuations; thus, in the last quarter of a century, the
speed of the equatorial current has progressively diminished. In 1879,
the velocity was 9 hours, 49 minutes, 59 seconds, and now it is, as we
have already seen, 9 hours, 50 minutes, 29 seconds, which represents a
substantial reduction. The rotation of the red patch, at 25 degrees of
the southern latitude, is effected in 9 hours, 55 minutes, 40 seconds.

We are confronted with a strange and mysterious world. It is the world
of the future.

This giant gravitates in space accompanied by a suite of five
satellites. These are:

Names. Distance from surface of Jupiter.