For weeks the work went on. Five separate shafts were sunk into the ground, the first four of them reaching down to the solid stratum of fire rock, below the lowest and oldest fossil levels. From the depths of those first four shafts the drill brought up pieces of stone, some of which had angular corners, like carven blocks. And there were great lumps of rust too, that might have been reenforcing bars of steel. Thus the mystery deepened, taking on qualities of nervous unrest and expectancy. And then, far down in the fifth shaft, the spinning diamond points of the drill snarled into a new medium. An hour later, in the summer dusk, Roderick Murgatroyd stood shifting a few ounces of muck, brought up from the excavation, back and forth between his palms. Most of it was grey volcanic stuff, but mingled with it were long shreds of metal, scored out by the drillpoints. The metal was as soft and pliable as lead, but it possessed a very considerable tensile strength. Tests had already proved that it was lead, alloyed with certain rare-earth elements, probably to increase its toughness, and to render it immune to the ravages of time. "It's true, Perry," Murgatroyd said very quietly to the younger man beside him. "Truer than we could have quite understood before. Metal down there shows that. A carefully prepared alloy, such as only a very well developed metallurgical science could have produced. A layer, or a shell. Or maybe just a block. We don't know yet. "Yes, we're on the right trail, Perry, even if it does look like a wild trail! Only yesterday the drill brought up fossils of an _undisturbed_ stratum belonging to the Jurassic Period, the Age of Reptiles many millions of years ago! That means, Perry--" and the old Scotch-American's voice was still more vibrant and tense--"that means that this lead alloy was made and put into place before--long before--the time of the dinosaurs. In fact, if we are to judge from the stratum immediately surrounding the metal, it is contemporary with the Carboniferous Era or Coal Period. That's the point, Perry. There weren't any men on this planet at that time. And there weren't going to be any men for ages and ages. At least not Earth men...." Perry Wilcox nodded, controlling his own taut nerves. They were right at the edge of a staggering discovery, he was sure. It might break any minute, now, or any hour. The drill machinery still vibrated, boring into that mass of metal deep in the ground. The pumps, sucking seepage water out of the excavation, still throbbed. The two men's ears were tuned to the sound of the machinery. Any shift or change in the regular beat of the drill would have a story to tell. Thus they waited, as night began to fall, slowly but surely. * * * * *