“I felt an earth tremor last night,” said Bickley, “though it is odd that it should only have affected this particular statue. A thousand pities, for it was a wonderful work of art.” Then I remembered and reminded Bickley of the crash which we had heard while Yva and Bastin were absent on some secret business in the chamber. Walking the length of the great church, if so it could be called, we came to an apse at the head of it where, had it been Christian, the altar would have stood. In this apse was a little open door through which we passed. Beyond it lay a space of rough rock that looked as though it had been partially prepared for the erection of buildings and then abandoned. All this space was lighted, however, like the rest of the City of Nyo, and in the same mysterious way. Led by Yva, we threaded our path between the rough stones, following a steep downward slope. Thus we walked for perhaps half a mile, till at length we came to the mouth of a huge pit that must, I imagine, have lain quite a thousand feet below the level of the temple. I looked over the edge of this pit and shrank back terrified. It seemed to be bottomless. Moreover, a great wind rushed up it with a roaring sound like to that of an angry sea. Or rather there were two winds, perhaps draughts would be a better term, if I may apply it to an air movement of so fierce and terrible a nature. One of these rushed up the pit, and one rushed down. Or it may have been that the up rush alternated with the down rush. Really it is impossible to say. “What is this place?” I asked, clinging to the others and shrinking back in alarm from its sheer edge and bottomless depth, for that this was enormous we could see by the shaft of light which flowed downwards farther than the eye could follow. “It is a vent up and down which air passes from and to the central hollows of the earth,” Yva answered. “Doubtless in the beginning through it travelled that mighty force which blew out these caves in the heated rocks, as the craftsman blows out glass.” “I understand,” said Bastin. “Just like one blows out a bubble on a pipe, only on a larger scale. Well, it is very interesting, but I have seen enough of it. Also I am afraid of being blown away.” “I fear that you must see more,” answered Yva with a smile, “since we are about to descend this pit.” “Do you mean that we are to go down that hole, and if so, how? I don’t see any lift, or moving staircase, or anything of that sort.” “Easily and safely enough, Bastin. See.” As she spoke a great flat rock of the size of a small room appeared, borne upwards, as I suppose, by the terrific draught which roared past us on its upward course. When it reached the lip of the shaft, it hung a little while, then moved across and began to descend with such incredible swiftness that in a few seconds it had vanished from view.