The consequences
that the observers deduce from the fact are interesting. The
sun-baked half of Venus seems to be devoid of water or vapour,
and it is thought that all its water is gathered into a rigid
ice-field on the dark side of the globe, from which fierce
hurricanes must blow incessantly. It is a Sahara, or a desert far
hotter than the Sahara, on one side; an arctic region on the
other. It does not seem to be a world fitted for the support of
any kind of life that we can imagine.
When we turn to the consideration of Mars, we enter a world of
unending controversy. With little more than half the diameter of
the earth, Mars ought to be in a far more advanced stage of
either life or decay, but its condition has not yet been
established. Some hold that it has a considerable atmosphere;
others that it is too small a globe to have retained a layer of
gas. Professor Poynting believes that its temperature is below
the freezing-point of water all over the globe; many others, if
not the majority of observers, hold that the white cap we see at
its poles is a mass of ice and snow, or at least a thick coat of
hoar-frost, and that it melts at the edges as the springtime of
Mars comes round.
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