"That kills the theory about eighty feet of that stuff, anyway," said Sam as he read the instruments. Jim was not interested in depth at this time. He fed some of the surface material into the laboratory and set the controls to run the preprogrammed analysis. They waited minutes; then the analysis began to appear in cryptic symbols on a paper tape. Jim glanced at it and frowned. "What's the matter? Isn't it working right?" Sam asked anxiously. Jim hesitated. "It indicates the presence of several silicates, some carbonates, and a high percentage of oxides. These are mostly of sodium, calcium, and iron, as you might expect. But there's something wrong with your calibration. The atomic and molecular characteristics aren't coming through right." "The boys ran checks on the standard samples aboard the Prospector last night," said Sam. "The results tallied exactly. I'll show you the tapes." * * * * * Jim waited, puzzled, while Sam brought up the check tapes. When he saw them, he shook his head. "There's a standard calcium carbonate sample carried aboard the Prospector. Here's a calcium carbonate picked off the surface. You can see the difference yourself. The nominal analysis is the same, but the atomic weights and the energy levels are just slightly different. That doesn't make sense unless your circuits are out of calibration." "Let's run another standard sample," said Sam. Within a few minutes the calibration check had been repeated. Jim held up the tape. Sam peered over his shoulder. "Just like the first one," said Sam. "Nothing's wrong with the circuits. Maybe you've got some new stuff there, that's never been identified before." "That's hardly possible," said Jim. "There aren't any new elements in the places where sodium and calcium and silica are supposed to be. Yet, I don't understand how this can be. If the atomic weights are different, and the energy levels are different, they have to be different elements. It doesn't make sense." "Well, why don't we push on," said Sam, "that is, if you've completed the surface sampling in this spot. Some samples at lower depths may give other indications." Jim agreed. He drove the drill deeper into the face of the moon. At ten-foot intervals he removed samples and ran them through the analyzer. The results were the same down to the hundred-foot level. All results showed common chemical elements with slightly variant atomic characteristics. Which made them _different_ chemical elements! After six hours, Jim stood up from the console and shook his head wearily. "It's no good, Sam. There's something wrong that I can't put my finger on. If it isn't in the circuits, I don't know where it is. But these readings just aren't right. There's no use going deeper until we find out where the error is." Sam's face was somber. "There just isn't any error. There can't be. Unless it was made by whoever put the moon together--"