"Yes, and the machine is now here; the men are at work setting it up; so we might as well go over and help out." A second invitation was not necessary. Ralph, who was outside in one bound, rushed across the field, but Alfred accompanied the lieutenant to the commandant's office, where they were provided with the receipt for the machine. The lieutenant remained here while Alfred carried the document to the warehouse. Within two hours the machine was in condition to receive the fuel and the supplies usually carried in the machines for emergencies. When the lieutenant returned he made a careful inspection, and on this occasion the boys followed every movement of his to learn what were the essential requirements in inspecting. Naturally, the most important thing was to know that every part of the frame is not only properly set up and the wires made taut, but that the fastenings, the turnbuckles, are in good condition. That necessitated a minute examination of every one of them. Then the planes were sighted to ascertain whether they were properly aligned. Sometimes when the planes are not exactly parallel with each other, the end of one, for instance, being set a little higher or lower than the other, it is usually corrected by letting out one or more sets of brace wires and taking up on others. This observation was followed by a careful look at the control planes. These are the sensitive parts of the plane, and may be likened to feelers, for the slightest warping of the horizontal tail planes will frequently cause the machine to fly with a skidding motion, not dangerous, but exceedingly uncomfortable when flying at a high rate of speed. "The wires leading to the control levers are always a source of worry to me," remarked the lieutenant, and he drew himself up into the rear part of the chassis. "You will notice that this one rubs along the side of that brace. I could not permit that," he said, as he glanced toward one of the workers. "Do you think it would weaken the brace?" asked Ralph. "No, it's not that," replied the lieutenant. "The difficulty is that all these wires are stranded, and as soon as one of the wires wears out by the frictional contact, another will give way, and the control wire is liable to part at the most critical time." The boys had occasion to remember the lieutenant's warning shortly thereafter. After an examination of the airplane structure an investigation was made of the engine. The mechanic turned it over to be sure that the compression was all right. Self-starters are provided on all these machines, as the French learned at an early day that it would be unwise to depend on cranking. Then a thorough inspection of the pipes and tubing for the fuel and lubrication was made. The dashboard of an aeroplane is a much more wonderful contrivance than the dashboard of an automobile. The aviator must look out for several things not necessary when traveling on land.