d again in 1891, rotated in 9h. 48m. to 9h. 49-1/2m. It may,
therefore, be regarded as certain that the globe of Jupiter, so far as
we can see it, is not a solid body. It consists, on the exterior at all
events, of clouds and vaporous masses, which seem to be agitated by
storms of the utmost intensity, if we are to judge from the ceaseless
changes of the planet's surface.

[Illustration: PLATE XI.

Feb. 2nd. Feb. 4th.

Feb. 12th. Feb. 28th.

THE PLANET JUPITER.

1897.]

[Illustration: Fig. 57.--The Occultation of Jupiter (1).]

[Illustration: Fig. 58.--The Occultation of Jupiter (2).]

[Illustration: Fig. 59.--The Occultation of Jupiter (3).]

[Illustration: Fig. 60.--The Occultation of Jupiter (4).]

Various photographs of Jupiter have been obtained; those which have been
taken at the Lick Observatory being specially interesting and
instructive. Pictures of the planet obtained with the camera in
remarkable circumstances are represented in Figs. 57-60, which were
taken by Professor Wm. H. Pickering at Arequipa, Peru, on the 12th of
August, 1892.[21] The small object with the belts is the planet Jupiter.
The large advancing disc (of which only a small part can be shown) is
the moon. The phenomenon illustrated is called the "occultation" of the
planet. The planet is half-way behind the moon in Fig. 59, while in Fig.
60 half of the planet is still hidden by the dark limb of the moon.

It is well known that the tempests by which the atmosphere surrounding
the earth is convulsed are to be ultimately attributed to the heat of
the sun. It is the rays from the great luminary which, striking on the
vast continents, warm the air in contact therewith. This heated air
becomes lighter, and rises, while air to supply its place must flow in
along the surface. The currents so produced form a breeze or a wind;
while, under exceptional circumstances, we have the phenomena of
cyclones and hurricanes, all originated by the sun's heat. Need we add
that the rains, which so often accompany the storms, have also arisen
from the solar beams, which have distilled from the wide expanse of
ocean the moisture by which the earth is refreshed?

The storms on Jupiter seem to be vastly greater than those on the earth.
Yet the intensity of the sun's heat on Jupiter is only a mere
fraction--less, indeed, than the twenty-fifth part--of that received by
the earth. It is incredible that the motive power of the appalling
tempests on the great