It was their lookout not mine, however, and still intent on tracing the water to its source I turned up a trail that appeared to lead to the mountain top. In places this was excessively steep and here Zip exhibited a new habit of his people. Dropping his feet he proceeded to climb the path on all fours, his feet first and his prehensile toes grasping every projection and bit of rock to draw him along while his immense, powerful hands supported his weight and pushed him onward. He looked more like a gigantic spider than anything, and not in the least human. Panting and blown I at last gained the summit and looked down upon a lake of dismal black water filling a circular crater about half a mile in diameter. Close by was an aperture in the rock and half-filled with water, and it was evident that this was connected with the outlet below by means of a shaft. Whether this was a natural formation or had been laboriously cut by hand I could not tell, but I was prepared for almost anything by this time and was not greatly surprised to find a cleverly constructed sluice gate arranged above the opening to regulate the flow of water. I had seen similar crater lakes in the extinct volcanoes of the West Indies, but I was surprised that Hazen had not mentioned it. But on second thought I realized that when flying over it, the dark water surrounded by vegetation would hardly be visible and might easily be mistaken for heavy shadow or an empty crater, while the aviator’s surprise at the city would fix his attention upon it to the exclusion of all surroundings. Standing upon the rock ridge several hundred feet above the city I had almost the same view as Hazen had from his plane and I could understand how, at an elevation of 5000 feet or more, he had been unable to obtain any very accurate idea of the buildings or people. I also realized, with a sinking of my heart, that it would be next to impossible for him to recognize me or to see any signals I might make. The most prominent spot in the entire valley was the pyramid, for this was isolated upon the green plain and the sun, striking through a gap in the eastern rim of the crater, shone directly upon the altar’s summit, thus bringing it out in sharp relief. Indeed, it looked for all the world like a pylon on an aviation field. If I expected to make my presence known to Hazen or to signal to him, my best point of vantage would be the summit of the pyramid and I determined to climb there and await his arrival when he should be due, two days later. Little did I dream at the time of the conditions under which I would await him upon that gruesome altar. CHAPTER IV THE SACRIFICE