al system, provision had to be made for suitable reservoirs
to impound the water after the seasonal thaws at the poles. To this
end immense reservoirs were constructed at most canal intersections.
In some instances the reservoirs are established between parallel
canals; but in every case smaller canals, or laterals, always intersect
at these points.

Many of the canals on Mars are double, as they appear to your
astronomers. These double waterways parallel each other at a distance
of about 75 miles. The reason for this is that as the Martian
population is absolutely dependent upon the Polar waters to irrigate
their crops, any accident to a canal, such as a landslide stopping the
regular flow of water or the breaking of a lock or gate, would mean a
very serious calamity to a great number of people. And for that
reason, soon after the main canals were constructed, second and
parallel waterways were made for the purpose of guaranteeing an
uninterrupted flow of water from the Poles to the Equatorial regions.
The result of this was that on many occasions the foresight of the
Martian engineers who had the water supply of the planet in charge,
saved immense areas from drought.

The rainfall on Mars is almost nil and the immense population (eight
times larger than that of your Earth) is entirely dependent on the
water supply from the melting Polar caps. Water on Mars is a most
precious fluid and there is none to waste. Our oceans evaporated ages
ago, and outside of the precipitation of moisture at the poles in the
form of snow, none is to be had anywhere else on the planet except in
very meager quantities.

The astronomer Lowell of your Earth, who made a life study of our
planet, called these reservoirs "Oases," but he was mistaken in his
theory. He concluded that these points, which appear as round disks in
the telescope, were centers of population. This conclusion is
erroneous. The centers of population on Mars are scattered over the
entire planet regardless of the position of the so-called "Oases." It
is quite true that owing to the rapid evaporation of water in the
comparatively thin atmosphere of Mars, the dewfall for quite a radius
from the center of the reservoirs is considerable, with the result that
vegetation springs up, giving the "Oases" the appearance of a diameter
of about 75 miles. The reservoirs are about 60 miles across and hold
millions of gallons of water.

The same explanation may be given of t