"Bless my hat-rack!" went on the eccentric man, "but Tom isn't at all like himself of late. He's working on some invention, I know that, but it's all I do know. He hasn't given me a hint of it."

"Nor me, nor any of his friends," added Ned. "And he acts so oddly about enlisting—doesn't want even to speak of it. How he got exempted I don't know, but I do know one thing, and that is Tom Swift is for Uncle Sam first, last and always!"

"Oh, of course!" agreed Mr. Damon. "Well, we'll soon know, I guess. We'd better start, Ned."

"It's useless to try to guess what it is Tom is up to. He has kept his secret well. The nearest any one has come to it was when Harry figured out that Tom had a band of giant elephants which he was fitting with coats of steel armor to go against the Germans," observed Ned, when he and Mr. Damon were on their way.

"Well, that mightn't be so bad," agreed Mr. Damon. "But—um—elephants—and wild giant ones, too! Bless my circus ticket, Ned! do you think we'd better go in that case?"

"Oh, Tom hasn't anything like that!" laughed Ned. "That was only Harry's crazy notion after he saw something big and ungainly careening about the enclosed yard of Shop Thirteen. Hello, there go Mary Nestor and her father!" and Ned pointed to the opposite side of the street where the girl and Mr. Nestor could be seen in the light of a street lamp.

"They're going out to see Tom's secret," said Mr. Damon. "There's plenty of room in my car. Let's ask them to go with us."

"Surely," agreed Ned, and a moment later he and Mary were in the rear seat while Mr. Damon and Mr. Nestor were in the front, Mr. Damon at the wheel, and they were soon speeding down the road.

"I do hope everything will go all right," observed Mary.

"What do you mean?" asked Ned.