he direct and blistering rays
of the sun, which is only 86,000,000 miles away. To Professor Lowell it
presents the appearance of a bleached and sun-cracked desert, or "the
bones of a dead world." Its temperature must be at least 300 degrees C.
above that of the earth. Its features are what we should expect on the
nebular hypothesis. The slowness of its rotation is accounted for by
the heavy tidal influence of the sun. In the same way our moon has been
influenced by the earth, and our earth by the sun, in their movement of
rotation.

Venus, as might be expected in the case of so large a globe (nearly
as large as the earth), has an atmosphere, but it seems, like Mercury,
always to present the same face to the sun. Its comparative nearness
to the sun (67,000,000 miles) probably explains this advanced effect of
tidal action. 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. In regard to its famous canals we are no nearer agreement.
Some maintain that the markings are not really an objective feature;
some hold that they are due to volcanic activity, and that similar
markings are found on the moon; some believe that they are due to
clouds; while Professor Lowell and others stoutly adhere to the familiar
view that they are artificial canals, or the strips of vegetation along
such canals. The que