“The people of our planet have long been masters of electricity. In fact, it has been the only available source of power on Mars for centuries. This power is utilized to manipulate the valves in the various siphons which feed each canal, insuring its usefulness until the last portion of the polar cap is virtually exhausted. Accurate maps of all polar sea basins exist, of course. The pumping station nearest the pole, on each canal, has one of these maps indicating every siphon and valve feeding that canal. As the water from the nearest basin is exhausted, the valve of that feed is closed by manipulation of a corresponding switch in the station, and one of the other feeds is opened. A chart of the retrogression of the seas with the declining season enables the attendant to drain each sea basin completely in its proper turn as the melting snow recedes.” “Wonderful!” exclaimed Robert and Professor Palmer in unison. Taggert was busily scribbling in his notebook. In a short while the _Sphere_ had reached the edge of the snow-cap. Immediately below, and stretching away some distance to the south and west, was a small sea, still well filled but covered with a smooth sheet of ice which reflected the rays of the low sun in a blinding, yellow blaze. At the suggestion of their guide, Robert raised the _Sphere_ till it was perhaps a mile high. From this point of vantage they could see the full extent of the polar cap. It seemed to be about twenty-five miles in diameter. They fancied they could see some of the canals beyond its farthest edge, though they could not be certain, because of a slight murkiness in the atmosphere in that direction. Robert now lowered the _Sphere_ almost to the surface of the snow and for a time they hovered over various parts of the cap. Quite different was this polar region from that of the Earth, for it was almost entirely one continuous, level sheet of snow and ice, without the great, towering icebergs and the mountain peaks which we associate with the arctic regions of our own world. So far, their polar excursion had proved quite tame. Remembering the princess’ anxiety, Robert wondered whether it had been due entirely to imagination. He questioned the Martians as to the possible dangers of the region. They replied that, during the winter season, the region was noted for its sudden and terrific blizzards, which lasted for weeks at a time. According to them, the approaching winter was not expected to break for some weeks yet. By common consent, the _Sphere_ was landed on the shore of the sea which seemed to surround the shrunken cap. A layer of crystallike ice stretched off in three directions, unbroken except along the shore, where it was evident that the water beneath the ice was still being withdrawn, for the ice cakes were deposited in huge blocks on the sloping shore for several hundred yards beyond its present edge.