But to my surprise I ran against a blank wall before I reached a point where the waters came to the roof of the corridor. Could I be mistaken? I felt around. No, I had come to the main corridor, and still there was a breathing space between the surface of the water and the rocky ceiling above. And then I turned up the main corridor in the direction that Carthoris and the head of the column had passed a half-hour before. On and on I swam, my heart growing lighter at every stroke, for I knew that I was approaching closer and closer to the point where there would be no chance that the waters ahead could be deeper than they were about me. I was positive that I must soon feel the solid floor beneath my feet again and that once more my chance would come to reach the Temple of Issus and the side of the fair prisoner who languished there.
But even as hope was at its highest I felt the sudden shock of contact as my head struck the rocks above. The worst, then, had come to me. I had reached one of those rare places where a Martian tunnel dips suddenly to a lower level.