Its sides were smooth and polished, and the light seemed to come not from their surfaces, but from far within them--giving to the walls an illusive aspect of distance and depth; rendering them in a peculiarly weird way--spacious.

The passage turned, twisted, ran down, turned again.

It came to me that the light that illumined the tunnel was given out by tiny points deep within the stone, sprang from the points ripplingly and spread upon their polished faces.
There was a cry from Larry far ahead.
"Olaf!" I gripped Marakinoff's arm closer and we sped on.

Now we were coming fast to the end of the passage.

Before us was a high arch, and through it I glimpsed a dim, shifting luminosity as of mist filled with rainbows.