I answered, “I see the point you make, and I agree that I was inclined to a too-hasty assumption. Also, it enters my mind that if the earth be indeed hollow at a depth of a few hundred miles, and an inner surface be land only, it must be of far greater extent, not merely than this continent, but than the whole of the solid land of the earth’s surface as I knew it, and as it appears to be to-day. It is also possible to imagine tiers of hollowed space in which such areas might be many times repeated, but the artificial creation of such tiers would require an amount of labour which appears stupendous and the dumping on the earth’s surface of excavated material to an incredible volume.” She responded, “All that you think appears reasonable, and part is new to my mind. It would help us greatly if we knew whether the Dwellers are a numerous race, but of this I am able to tell you little. “Before the time of the Great War, we believe that they dwelt on the surface only, or, at least, until a comparatively short period before it. Up to that time, for reasons into which I must not now enter, being irrelevant, we knew little of them, or they of us. That was about eleven thousand years ago. “We know that they are bi-sexual, like the race from which you come. We suspect that their bodies age and decay, and are replaced by others, but of this we have no certain knowledge. “In all the time I mention I cannot recall having seen more than two hundred of their men and three of their women. We do not suppose that they exist in these proportions. Our observation of the sea-creatures is that they cannot dwell in peace together unless their females are at least equally numerous, but we have seen those only who first negotiated the treaty with our Leaders, of which you have been told, and such as have been in attendance at the fish-tanks. Of these I mention, I cannot recall that more than thirty have been seen at any one period. As the centuries have passed, there has been a gradual change. But this might only mean that they have exchanged to other duties. I have never seen one that showed signs of age, nor that was less than full-grown. The eight which we saw last night I had not seen previously.” I answered, “But, even in the absence of more direct evidence, the works which we have seen suggest that they are a numerous race. “The protective belt which surrounds the continent cannot be less than five thousand miles in length, and it was twelve miles in breadth at the point at which we crossed it. Even for giants such as they, it would be an impossible task for a small community. Then we see that they patrol the coast, which must be the work of many.”