"I'll be on the watch," said Tom. And, as he went into his private workshop, he wondered why it was his father and Ned had both warned him not to trust Gale and Ware.
The next few days were busy ones for Tom Swift. Once he had made up his mind to go to work seriously on a silent motor, all else was put aside. He sent a note to Mary Nestor, telling her what he was going to do, and, asking her to say nothing about it, which, of course, Mary agreed to.
"Come and see me when you can," she sent back word, "but I know you won't have much chance when you're experimenting with your invention. And I shall be working so hard for the Red Cross that I sha'n't get much chance to entertain you. But the war can't last forever."
"No," agreed Tom with a sigh, as he put away her letter, "and thank goodness that it can't!"
The young inventor threw himself into the perplexing work of inventing a silent motor with all the fervor he had given to the production of his war tank, his giant cannon, his wonderful searchlight and other machines.
"And," mused Tom, as he sat at his work table with pencil and paper before him, "since this is a problem in acoustics, I had best begin I suppose by going back to first principles, and after determining what makes an aeroplane engine noisy, try to figure out how to make it quiet. Now as to the first, the principle causes of noise are—"
And at that instant there broke on Tom's ears a succession of discordant sounds which seemed to be a combination of an Indian's war whoop and a college student's yells at a football game.
"Now I wonder what that is!" mused the young inventor as he hastily arose. "Better solve that problem before I tackle the aeroplane motor."