"If, as has been contended, the loss by evaporation would be so great in canals where the water is fairly deep as to result in depletion of the supply, it is clear there must be a hundred times greater loss from the same cause if the water is allowed to spread in a very shallow pool over a large area where it would be totally unprotected from the sun! Then, again, every part of our planet not reached by the water would become desert.
"No, sir," Tellurio added, "the Martians are far too intelligent to waste the water in this fashion: hence their canal system by which the water is economically distributed where required, and also protected from undue evaporation. It must not be forgotten that our canals are also means of communication across the deserts, and without them distant parts of the planet would 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 satisfactory, it will be possible to see lines on the planet which are not more than one mile in width.
As regards the surface characteristics of Mars, we found that it is generally very flat, and that only here and there one comes across slight undulations, whilst hills and mountains are very few indeed. There are, in fact, no high mountains anywhere; the highest altitudes rarely approach 2000 feet, and such heights as these are quite exceptional.