Contrary to many ingenious speculations which have been indulged in by both scientist and romancer, they found that the hemisphere, which for countless ages had never been turned towards the earth, was almost an exact replica of the visible one. Fully three-fourths of it was brilliantly illuminated by the sun, and what they saw through their glasses was practically the same as what they had beheld on the earthward side; huge groups of enormous craters and ringed mountains, long, irregular chains crowned with sharp, splintery peaks, and between these vast, deeply depressed areas, ranging in colour from dazzling white to grey-brown, marking the beds of the vanished lunar seas. As they crossed one of these, Redgrave allowed the _Astronef_ to sink to within a few thousand feet of the surface, and then he and Zaidie swept it with their telescopes. Their chance search was rewarded by something they had not seen in the sea-beds of the other hemisphere. These depressions were far deeper than the others, evidently many thousands of feet below the average surface, but the sun's rays were blazing full into this one, and, dotted round its slopes at varying elevations, they made out little patches which seemed to differ from the general surface. "I wonder if those are the remains of cities," said Zaidie. "Isn't it possible that the old peoples of the moon might have built their cities along the seas just as we do, and that their descendants may have followed the waters as they retreated, I mean as they either dried up or disappeared into the centre?" "Very probable indeed, dearest of philosophers," he said, picking her up with one arm and kissing the smiling lips which had just uttered this most reasonable deduction. "Now we'll go down and see." He diminished the vertically repulsive force a little, and the _Astronef_ dropped slantingly towards the bed of what might once have been the Pacific of the Moon. When they were within about a couple of thousand feet of the surface it became perfectly plain that Zaidie was correct in her hypothesis. The vast sea floor was thickly strewn with the ruins of countless cities and towns, which had been inhabited by an equally countless series of generations of men and women, who had perhaps lived and loved in the days when our own world was a glowing mass of molten rock, surrounded by the envelope of vapours which has since condensed to form our oceans. They dropped still lower and ran diagonally across the ocean-bed, and as they did so Zaidie's proposition was more and more completely confirmed, for they saw that the towns and cities which stood highest were the most dilapidated, and that the buildings had evidently been torn and crumbled away by the action of wind and water, snow and ice.