There was no visible outlet for the silver liquid; so I knew that it must find its way off underground. I knew that we must be far below the level of the Silver Lake and the plain beyond. That fact may have accounted for the more luxuriant growth of the red vegetation. Suddenly Naro reported the discovery of the comparatively fresh print of a hob-nailed boot in a little patch of mould on the rock. That set us to looking again for traces of Austen, and presently we found a fairly well-defined trail that led off to the east. We followed it eagerly. When we had gone perhaps a mile we came to an outcropping seam of coal. There I found the plain marks of a copper pick. Evidently a good deal of coal had been dug up and carried off down the trail. CHAPTER X Austen's Retreat Perhaps two hundred yards farther on we came to the camp. It was on a little hilltop below a giant tree. By the trunk was a little mud-daubed hut, with an open shed in front of it. By the shed was a rude clay furnace, with piles of coal, some strange ore, and large lumps of native copper lying by it. Beneath the shed was what appeared to be a small steam turbine, with a kettle-like boiler of hammered copper. Connected with it was a dynamo of crude but ingenious construction. Also there was a rude forge, and hammers, anvils, saws and drills, all of copper or bronze, and a device that I supposed had been used for drawing wire. Simple as it seemed, that camp of Austen's was perhaps the most remarkable thing I came across in the crater. Austen was a wonderful man. Having not only an exhaustive knowledge of a half dozen fields of science--and he had not mere theories, but a practical, working knowledge--he had also courage and determination, patience and manual skill, and a great deal of resourcefulness and invention. While the average man would hardly have been able to keep alive in the jungle, Austen was able to do such things as smelt and refine ore, and set up complicated and workable electrical machinery. Of course he was fortunate in finding himself in a place where practically no effort was needed to satisfy his physical needs, and where he found various natural resources in available and easily accessible form. But I shall never cease to wonder at his accomplishments of less than a year. I was struck by a sudden fear that we had come too late, and that something had happened to him. "Austen," I shouted, "Austen, are you here?"