“In particular, you have shown me your mind, and I have seen that you visualise an end to these tunnels which opens into a hall, a chamber, or a large passage, or at least some public space, populated by the Dwellers, and where concealment for ourselves would be difficult, if not impossible. Your imagination may be correct, and it is a possibility for which we must be prepared. But in your mind it is less a possibility than an expectation, for which there is no sufficient ground whatever. Yet you had imagined it so confidently that I had difficulty in separating it from the facts you had shown me. “I thought of this very long, and I see that your life is so brief, and so confusingly occupied, that you are obliged to proceed through a labyrinth of assumptions by which you hope to reach the thing you wish more rapidly than would otherwise be possible. But in this case, I cannot see that the assumption has any basis of probability. “I know, from what you have shown me already, that you come of a race which has lived only on the earth’s surface, and any cave or tunnel by which you enter it implies the approach to a confined and narrow space, so that when you attempt to visualise the condition of a race which lives under the surface, your imagination is of a cave, and not of a country. “Now if the interior of the earth be completely solid, or nearly so, this imagination may be quite accurate. But is it? Neither of us knows. We do know from your own experience that the tunnels go down for many miles, though we do not know their ultimate depth. That suggests that there must be some reason for so deep a penetration. To make such tunnels must have been a great labour. To descend and ascend them continually must be an unceasing toil. There must be some compensating advantage in the depth which is reached. The hollowness of the interior would supply it. But there might be quite different reasons. We know that there are areas of great heat that lie closely under the surface. There are parts of the ocean floor where this heat causes eruptions. Such areas may be of great extent. They may render it difficult or impossible to live under the surface till a greater depth is reached. True, the tunnels must penetrate this region, on this supposition, and it must therefore have been found possible to render them heat-proof. “We have one other fact. The Dwellers reach the surface at very distant points. But this has no certain significance.”