"Yes, I will explain to you. I have already told you, and, in fact, you must have seen it for yourselves, that there are almost no mountains on Mars. A very learned man of my race used to say that the reason was because Mars is so very old a world that the mountains it once had have been almost completely levelled, and the entire surface of the planet had become a great plain. There are depressions, however, most of which are occupied by the seas. The greater part of the land lies below the level of the oceans. In order at the same time to irrigate the soil and make it fruitful, and to protect themselves from overflows by the ocean breaking in upon them, the Martians have constructed the immense and innumerable canals which you see running in all directions over the continents." "There is one period in the year, and that period has now arrived, when there is special danger of a great deluge. Most of the oceans of Mars lie in the southern hemisphere. When it is Summer in that hemisphere, the great masses of ice and snow collected around the south pole melt rapidly away." "Yes, that is so," broke in one of our astronomers, who was listening attentively. "Many a time I have seen the vast snow fields around the southern pole of Mars completely disappear as the Summer sun rose high upon them." "With the melting of these snows," continued Aina, "a rapid rise in the level of the water in the southern oceans occurs. On the side facing these oceans the continents of Mars are sufficiently elevated to prevent an overflow, but nearer the equator the level of the land sinks lower." "With your telescopes you have no doubt noticed that there is a great bending sea connecting the oceans of the south with those of the north and running through the midst of the continents." "Quite so," said the astronomer who had spoken before, "we call it the Syrtis Major." "That long narrow sea," Aina went on, "forms a great channel through which the flood of waters caused by the melting of the southern polar snows flows swiftly toward the equator and then on toward the north until it reaches the sea basins which exist there. At that point it is rapidly turned into ice and snow, because, of course, while it is Summer in the southern hemisphere it is Winter in the northern." Mars Will Be Ours. "The Syrtis Major (I am giving our name to the channel of communication in place of that by which the girl called it) is like a great safety valve, which, by permitting the waters to flow northward, saves the continents from inundation." "But when mid-Summer arrives, the snows around the pole having been completely melted away, the flood ceases and the water begins to recede. At this time, but for a device which the Martians have employed, the canals connected with the oceans would run dry, and the vegetation, left without moisture under the Summer sun, would quickly perish."