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 rather surprised not to have come across any comment by our scientists on the significance of this very large increase of fertile land, as, taken in connection with the great canal system, it seemed to me very significant and full of meaning.
Merna, continuing his remarks, then said that "Lately considerable extensions of their canal system had been carried out. New canals had been dug, others altered or extended, and vast areas had been considerably changed by replanting in some places and fallowing in others. The result of all this work," he said, "would produce a striking alteration in the configuration of some of the dark areas. Such changes," he remarked, "were carried out very rapidly, so rapidly indeed that it would probably be almost incredible to terrestrials; but it must be remembered that excavation, loading and removal of soil, as well as most other operations, were accomplished by special machinery. He had no doubt these changes would be noted by our observers, as Mars was so favourably situated in regard to the earth at the present time. Besides this," he continued, "many of our canals have been dealt with, and some of them will disappear, either temporarily or permanently."
"Well, Merna," said John, "if that is the case our observers will soon miss them; and I can imagine some of them gazing on your planet through their telescopes and exclaiming, 'Lo! here is the symbol of the death of Mars. Where we used to see canals there is now only blank space; the canals are disappearing, and the Martians must be rapidly decreasing in numbers and no longer able to maintain their vast canal system; or perhaps their water supply is diminishing so rapidly that it is becoming insufficient to keep the canals in working order; so ere long all life upon Mars must come to an end!'"
"If that should be so," said Merna, "they will be altogether wrong in their surmises, for the disappearance of several of our canals will not indicate death but life. Some of those canals will only be temporarily put out of use, but others, having served their purpose, will be discontinued permanently. They are like our flowers that have done blooming, which may be allowed to grow again next season, or the ground may be fallowed and fresh flowers planted elsewhere; so the vanished canals may be succeeded by fresh ones where they are needed; and when your people see these new canals they will know that they indicate the continued existence of vigorous and enterprising life upon Mars."
We then started upon our return home, and on the way I drew M'Allister's attention to the smaller size of the sun as we saw it now as compared with the size it appeared to us when on the earth. I told him that Mars was then about 131,000,000 miles from the sun, so the sun's apparent diameter was only about 221⁄4 minutes.
On the earth that day the sun's apparent diameter would be about 32 minutes. So to the Martians the sun only appeared about two-thirds the size it appeared to the people on the earth.
When, on 13th August this year, Mars was at its "perihelion," or nearest point to the sun, the latter was 129,500,000 miles distant, and would appear rather more than 221⁄2 minutes in diameter.
At the opposite point of its orbit, where it will be in "aphelion," or farthest from the sun, the sun will only appear about 19 minutes in diameter.
I then explained that, although the sun is so distant, Mars receives a very much larger percentage of the total heat and light available than we do on the earth, because of the thinness and generally cloudless condition of the atmosphere. It is estimated that our atmosphere and clouds shut out nearly 50 per cent. of the light and heat which would otherwise reach us in the course of the year. On the other hand, their "blanketing" effect considerably lessens the amount of heat radiated into space; thus, by keeping in the heat we have received, compensating to some extent for the original loss in quantity.