stion of the actual habitation of Mars is still
open. We can say only that there is strong evidence of its possession of
the conditions of life in some degree, and that living things, even on
the earth, display a remarkable power of adaptation to widely differing
conditions.

Passing over the 700 planetoids, which circulate between Mars and
Jupiter, and for which we may account either by the absence of one
large nucleus in that part of the nebulous stream or by the disturbing
influence of Jupiter, we come to the largest planet of the system. Here
we find a surprising confirmation of the theory of planetary development
which we are following. Three hundred times heavier than the earth
(or more than a trillion tons in weight), yet a thousand times less
in volume than the sun, Jupiter ought, if our theory is correct, to be
still red-hot. All the evidence conspires to suggest that it is. It has
long been recognised that the shining disk of the planet is not a solid,
but a cloud, surface. This impenetrable mass of cloud or vapour is drawn
out in streams or belts from side to side, as the giant globe turns on
its axis once in every ten hours. We cannot say if, or to what extent,
these clouds consist of water-vapour. We can conclude only that this
mantle of Jupiter is "a seething cauldron of vapours" (Lowell), and
that, if the body beneath is solid, it must be very hot. A large red
area, at one time 30,000 miles long, has more or less persisted on the
surface for several decades, and it is generally interpreted, either as
a red-hot surface, or as a vast volcanic vent, reflecting its glow upon
the clouds. Indeed, the keen American observers, with their powerful
telescopes, have detected a cherry-red glow on the edges of the
cloud-belts across the disk; and more recent observation with the
spectroscope seems to prove that Jupiter emits light from its surface
analogous to that of the red stars. The conspicuous flattening of its
poles is another feature that science would expect in a rapidly rotating
liquid globe. In a word, Jupiter seems to be in the last stage of
stellar development. Such, at some remote time, was our earth; such one
day will be the sun.

The neighbouring planet Saturn supports the conclusion. Here again we
have a gigantic globe, 28,000 miles in diameter, turning on its axis
in the short space of ten hours; and here again we find the conspicuous
flattening of the poles, the trailing belts of massed vapour acros