"I thought you owned a launch?" said Jack.
"Father bought me one," was the reply, "but I've never learned how to run it. I'm too fat to bother my head about such things!"
"Then what are you asking me about the mechanism of the thing for?" asked Jack. "If you don't want to know, what's the use of my telling you how to run a motor boat? You make me weary!"
"If I had a nice little temper like yours," Frank grinned, "I'd go and bump my head against a tree! Come, old man, tell me about the boat. I may want to run it some time, after you get caught by a cat or filled full of poisoned arrows! Come! honest! What makes it go?"
"And you don't even know the action of a gasoline engine?" exclaimed Jack, in better humor. "Well, I'll tell you. A jet of gasoline, which is thinner than water, is sprayed, as one would spray any liquid from an atomizer, into the chamber of the engine cylinder-head, which it reaches in the form of vapor, having been mixed with air."
"That's all simple!"
"Here the vapor is compressed by the rising piston, and when it is squeezed up as close as it can be an electric spark is introduced into the chamber. That is what the electric battery and gear are for."
"I was wondering why one had to have electricity and gasoline both," said Frank, very much interested in the simple recital.
"The result of the introduction of the spark is the explosion of the compressed vapor, which sends the piston downward. The motion turns the shaft, and that turns the boat's propeller."
"Easy as pie."