Presently we commenced the descent of a very steep incline.
"It will not be long," he said, "before we shall have light. At the lower levels we meet the same strata of phosphorescent rock that illuminates Omean."
Never shall I forget that trip through the pits of Issus. While it was devoid of important incidents yet it was filled for me with a strange charm of excitement and adventure which I think must have hinged principally on the unguessable antiquity of these long-forgotten corridors. The things which the Stygian darkness hid from my objective eye could not have been half so wonderful as the pictures which my imagination wrought as it conjured to life again the ancient peoples of this dying world and set them once more to the labors, the intrigues, the mysteries and the cruelties which they had practiced to make their last stand against the swarming hordes of the dead sea bottoms that had driven them step by step to the uttermost pinnacle of the world where they were now intrenched behind an impenetrable barrier of superstition.
In addition to the green men there had been three principal races upon Barsoom. The blacks, the whites, and a race of yellow men. As the waters of the planet dried and the seas receded, all other resources dwindled until life upon the planet became a constant battle for survival.
