"Oh, yes; and then you would start to make an investigation at once without waiting for the engine to stop," said Alfred.
"Exactly; it is there as a warning, just as a headache is a warning that something is wrong, or a pain, which is nature's way to indicate that an investigation should be made without delay," answered the lieutenant with a nod.
Besides the foregoing, the dash had on it a watch. Now, a watch may be a convenient thing to have on an automobile, but it is not a necessity. On a scouting and observation plane it is one of the necessary implements. Alfred laughed, as he looked at the neat little clock face.
"I suppose," he said, "we could get along without that."
"Of course we could," answered the lieutenant. "But why get along without it when we now find it such a necessary element?"
"Necessary how?" asked Ralph, in surprise.
"In determining distances, for one thing," answered the lieutenant.
"A watch to tell the distance?" asked Alfred incredulously.
"Yes, indeed," responded the lieutenant. "If you saw a puff of smoke in the distance, and shortly thereafter heard a boom, the distance could be determined almost instantaneously by roughly calculating 1,200 feet for every second. You see, the clock there has a second hand, which is very plain, for that very purpose."
"But suppose there is a regular battle on, it would be hard to tell about the boom from any particular gun, wouldn't it?" asked Ralph.