be entirely isolated from the rest of our
world, except for our air-ships.

"Our canal system has been a matter of slow growth and development.
Beginning with the straightening of the beds of old rivers and narrow
channels connecting seas, the canals were then constructed where they
were most needed; but as time passed on, and our water supply from
rainfall became less and less, we were convinced of the necessity of
adopting a complete system of canalisation in anticipation of the time
when our polar snows would be our only source of supply. This was
gradually carried into effect, and even now additional canals are being
constructed to meet the requirements of places not reached by existing
canals.

"In order to secure the return of the water to the poles, and so ensure
a future supply, it is absolutely necessary that, wherever possible, the
water should be conveyed in open channels so as to allow evaporation to
take place, otherwise much would be lost by soakage into the soil."

"Thank you, sir," I said; "those statements meet another objection which
has been urged against the possibility of the canals existing; it
apparently being assumed that the whole system must have been carried
out simultaneously, and that the population of Mars would have been much
too small to admit of that being done."

"Our population is by no means small, sir, having regard to the size of
our planet; and the Martians, as intelligent beings, have always been in
the habit of looking well ahead to ascertain what provision would be
required to satisfy our prospective needs. Your people take far too
narrow a view of these matters."

Thus many controversial matters were satisfactorily cleared up by
statements of actual facts.

During our journeys over the planet we came across a large number of
canals in different parts which have apparently not yet been discovered
by our observers. These were not all narrow lines of canals, and many of
them were double ones, so our observers have more work yet before them
in finding out these lines and recording them on their charts.

Professor Lowell, who has made many experiments in order to determine
how distant a fine line of known thickness (such as a telegraph wire)
may be situated and yet remain visible to the sight under ordinary
atmospheric conditions for clear seeing, has come to the conclusion that
when Mars arrives at its most favourable position for observation, and
other conditions are satis