lopment of the vast irrigation system of the planet
parallel bands of cultivation have been established, one receiving its
water supply from the canals of the other, and consequently lagging a
little behind in visibility as the water slowly percolates through the
soil and awakens the vegetation. Or else, the character of the
vegetation itself may differ as between two such parallel bands, one
being supplied with plants that spring up and mature quickly when the
soil about their roots is moistened, while the plants in the twin band
respond more slowly to stimulation.

Objection has been made to the theory of the artificial origin of the
canals of Mars on the ground, already mentioned, that the work required
to construct them would be beyond the capacity of any race of creatures
resembling man. The reply that has been made to this is twofold. In the
first place, it should be remembered that the theory, as Mr. Lowell
presents it, does not assert that the visible lines are the actual
canals, but only that they are strips of territory intersected, like
Holland or the center of the plain of Lombardy, by innumerable
irrigation canals and ditches. To construct such works is clearly not an
impossible undertaking, although it does imply great industry and
concentration of effort.

In the second place, since the force of gravity on Mars is in the ratio
of only 38 to 100 compared with the earth's, it is evident that the
diminished weight of all bodies to be handled would give the inhabitants
of Mars an advantage over those of the earth in the performance of
manual labor, provided that they possess physical strength and activity
as great as ours. But, in consequence of this very fact of the slighter
force of gravity, a man upon Mars could attain a much greater size, and
consequently much greater muscular strength, than his fellows upon the
earth possess without being oppressed by his own weight. In other words,
as far as the force of gravity may be considered as the decisive factor,
Mars could be inhabited by giants fifteen feet tall, who would be
relatively just as active, and just as little impeded in their movements
by the weight of their bodies, as a six-footer is upon the earth. But
they would possess far more physical strength than we do, while, in
doing work, they would have much lighter materials to deal with.

Whether the theory that the canals of Mars really are canals is true or
not, at any rate there can now be no doub