"Oh, all right," replied Tom, with a laugh. "Well, we're not going far on this trip. What I want to do, most of all, is to test the guns, and see if the recoil check will work as well when we are aloft as it did down on the ground. You know a balloon isn't a very stable base for a gun, even one of light caliber."
"No, it certainly is not," agreed Lieutenant Marbury, "and I am interested in seeing how you will overcome the recoil."
"We'll have a test soon," announced Tom.
Meanwhile the Mars, having reached a considerable height, being up so far, in fact, that the village of Shopton could scarcely be distinguished, Tom set the signal that told the engine-room force to start the propellers. This would send them ahead.
Some of Tom's most trusted workmen formed the operating crew, the young inventor taking charge of the pilot-house himself.
"Well she seems to run all right," observed Lieutenant Marbury, as the big craft surged ahead just below a stratum of white, fleecy clouds.
"Yes, but not as fast as I'd like to see her go," Tom replied. "Of course the machinery is new, and it will take some little time for it to wear down smooth. I'll speed her up a little now."
They had been running for perhaps ten minutes when Tom shoved over the hand of an indicator that communicated with the engine-room from the pilot-house. At once the Mars increased her speed.
"She can do it!" cried Ned.
"Bless my-hat! I should say so!" cried Mr. Damon, for he was standing outside the pilot-house just then, on the "bridge," and the sudden increase of speed lifted his hat from his head.