Round or oblong spots, as distinguished from belts, are still more variable and transient.

The main belts themselves show great internal commotion, frequently splitting up, through a considerable part of their length, and sometimes apparently throwing out projections into the lighter equatorial zone, which occasionally resemble bridges, diagonally spanning the broad space between the belts.
[Illustration: JUPITER AS SEEN AT THE LICK OBSERVATORY IN 1889.

THE GREAT RED SPOT IS VISIBLE, TOGETHER WITH THE INDENTATION IN THE SOUTH BELT.] Perhaps the most puzzling phenomenon that has ever made its appearance on Jupiter is the celebrated "great red spot," which was first noticed in 1878, although it has since been shown to be probably identical with a similar spot seen in 1869, and possibly with one noticed in 1857.
This spot, soon after its discovery in 1878, became a clearly defined red oval, lying near the southern edge of the south belt in latitude about 30 deg.

Its length was nearly one third of the diameter of the disk and its width almost one quarter as great as its length.

Translated into terrestrial measure, it was about 30,000 miles long and 7,000 miles broad.
In 1879 it seemed to deepen in color until it became a truly wonderful object, its redness of hue irresistibly suggesting the idea that it was something hot and glowing.