The damaged airship seemed little the worse for the test to which she had been subjected, and made her way at good speed in the direction of Tom's home. Several little experiments were tried on the way back. They all worked well, and the only two problems Tom had to solve were the taking care of the recoil from the guns and finding out why the propeller had broken.
A safe landing was made, and the Mars once more put away in her hangar. Mr. Damon departed for his home, and Lieutenant Marbury again took up his residence in the Swift household.
"Well, Tom, how did it go?" asked his father.
"Not so very well. Too much recoil from the guns."
"I was afraid so. You had better drop this line of work, and go at something else."
"No, Dad!" Tom cried. "I'm going to make this work. I never had anything stump me yet, and I'm not going to begin now!"
"Well, that's a good spirit to show," said the aged inventor, with a shake of his head, "but I don't believe you'll succeed, Tom."
"Yes I will, Dad! You just wait."
Tom decided to begin on the problem of the propeller first, as that seemed more simple. He knew that the gun question would take longer.
"Just what are you trying to find out, Tom?" asked Ned, a few nights later, when he found his chum looking at the broken parts of the propeller.