Tom and Harry snatched up their sombreros, hurrying forth. Trotter was found readily, and was ordered to saddle three ponies. Tom busied himself in picking out the best leveling instrument in camp, while Hazelton secured the rods and a chain. Then the party set forth in Indian file, Tom riding in advance. A trot of half an hour brought them to Section Nineteen. Here Tom speedily adjusted his instrument, taking up his post over the first stake at the bottom of the hill. Leveling is not difficult work, though it calls for some judgment and a good deal of care. For instance, when Tom set his telescope exactly level and took a reading of the rod at the second stake, which Harry held, he read the height as eight feet and four inches. Then he trudged forward, carrying his instrument, while Trotter held his rod exactly perpendicular over the first stake. From the second stake Tom sighted back through his telescope, reading two feet three inches. The difference between these two readings was six feet and one inch, showing that, for the distance between first and second stakes the rise in the hillside was six feet one inch. Thereupon Reade turned and sighted, from stake number two to stake number three, noting in his book the reading he secured from the rod at number three. Once at number three he turned his telescope backward, taking a reading from Trotter’s rod at number two. Ten stakes were thus covered, and not only were the foresights and backsights read and recorded, but the distance between each pair of stakes was measured with the chain and the distances entered on the record. At stake number ten Tom halted. “Harry,” he directed, “you take Black’s leveling notes and hold them while I read my own notes. Stop me every time that you note a difference between the two records.” After that Harry steadily stopped his chum at every reading. By the time that they had finished the comparisons Hazelton’s face looked blank from sheer astonishment. “Why, every single one of Blacks foresights and backsights is wrong!” gasped Harry. “And yet Mr. Blaisdell reported that ’Gene Black is such a fine engineer.” Tom turned to make sure that Trotter was resting out of hearing before he replied: “Harry, Black isn’t such a fool as to bring in an absolutely wrong record of sights, and yet do it innocently. If he didn’t do it unintentionally, then he must have tangled the record purposely.” “But why should he do it purposely?” Harry insisted. “He would know that, sooner or later, his blunders or lies would be discovered, and that he would be discharged. Now, Black really wants to hold his job with this outfit.” “Does he?” asked Tom bluntly. “Why, what do you mean?” “I don’t know,” Reade confessed. “I never heard of any such bungle as this before by an engineer. Why, Harry, this hillside averages an eight and a third grade, yet Black’s field notes show it to be only a three per cent. grade. Hang it, the fellow must have played the trick purposely!”