ch 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 rea