h of water in the canals than would be the case
if they were all in use at once.

"Many of the canals are only required for irrigating seasonal crops; so
as soon as the requisite amount of moisture has been acquired by the
soil the water is turned from that canal into another one, passing
through an area where a later seasonal crop is to be grown. This
arrangement, moreover, applies not only to our double canals, but also
to very many of the series which you have regarded as single canals."

Thus the mysteries connected with Mars were being cleared up one after
the other; and having regard to the very simple and natural explanations
we received, we could not help laughing as we talked the matter over and
recalled the immense amount of discussion and wrangling which had
occurred amongst our scientific men in connection with these matters,
and especially at the difficulty they seemed to experience in believing
that the canals could exist at all. Then there were those charges and
theories of overstrained eyes, diplopia, and defective focussing, to say
nothing of other suggestions. Well, I will not say any more upon this
point.

In continuation of our discussion of the canal question, I asked
Tellurio "Whether the canals and irrigation system had been the means of
reclaiming any large areas of land which had previously been deserts?"

"Oh yes, sir," he answered, "that has been the case in many parts of
our world; some very large areas indeed which were once deserts have now
become very fertile. Quite apart from such reclamations, however, our
canals and irrigation systems have also effectually checked the spread
of desertism. If it had remained unchecked, probably by this time the
entire surface of our planet would have become a desert."

I then explained that I asked the question because our observers had
seen and noted upon their charts several large areas which seemed to
have become fertile. Thus, along the eastern side of Thaumasia it had
been noted that, during a period of about twenty-three years, the green
area had advanced at least 400 miles nearer to the place we called the
"Solar Lake." On measuring this area on the map it appeared to me that
at least 200,000 square miles which had previously been desert had
become fertile.

Similar extensions of vegetation had also been charted in several other
places, for instance, on the east side of the large area known to us as
"Syrtis Major." I had, however, been rathe