s reached. They are,
however, not in themselves sufficiently conspicuous to be separately
discerned from the earth by our telescopic observers.

Machinery for forcing the water along the canals is also provided at
most of the junctions everywhere on the planet. In this connection it
must be remembered that the water is carried by the canals from one
hemisphere to the other, and, after passing the equator, must therefore
move in a direction contrary to that of ordinary gravitation.

Thus at one season of the year the water passes from the north polar
regions down into the southern hemisphere, and at the opposite period of
the year it is carried in the same way from the south polar regions
right into the northern hemisphere.

Gravitation being almost non-effective as regards the flow of water on
Mars, the movement would be extremely slow everywhere were it not for
the machinery, which adds to the speed of the flow. The average rate of
the movement of the water in the canals is about fifty-one miles a day,
and it takes about fifty-two days for the water to pass from about
latitude 72 deg. down to the equator, a distance of 2650 miles.

This rate of flow, as indicated by the darkening arising from the growth
of vegetation which follows the flow of the water down the canals, has
been observed and noted many times at Flagstaff Observatory.

It was now perfectly clear to us why the "carets" are only seen in the
particular places in which they have been observed by Professor Lowell
and his colleagues. They are, in fact, only needed in connection with
water-lifting apparatus, and locks and weirs, at the places where
high-level canals connect with those at a lower level!

We were all very pleased at finding the solution of a problem which had
been much discussed between us without arriving at any satisfactory
conclusion.

John then asked Tellurio if he would be good enough to explain to us how
it was that our observers on the earth saw some of the Martian canals
doubled at some periods of the year and single at other times; and
sometimes one of the twin canals was seen alone, and at other times the
second one only was visible.

"It is a very simple matter, sir," replied Tellurio. "You will
understand that we do not wish to waste any of our water, and as it is
quite unnecessary to use all our canals at the same time, we only use
those which are actually required. This arrangement also allows us to
have a much greater dept