ontrol the magnets that hold the bombs in place. If I
press one of the buttons it breaks the electrical current, the magnet
no longer has any attraction, and it releases the explosive. Now look
down. I am going to try and drop a chalk bomb near that stone fence."

The Mars was then flying over a large field and a stone fence was in
plain view.

"Here she goes!" cried Tom, as he made some rapid calculations from his
gauge instruments. There was a little click and the chalk bomb dropped.
There was a plate glass floor in part of the cabin, and through this
the progress of the pasteboard bomb could be observed.

"She'll never go anywhere near the fence!" declared Ned. "You let it
drop too soon, Tom!"

"Did I? You just watch. I had to allow for the momentum that would be
given the bomb by the forward motion of the balloon."

Hardly had Tom spoken than a puff of white was seen on the very top of
the fence.

"There it goes?" cried the lieutenant. "You did the trick, Swift!"

"Yes, I thought I would. Well, that shows my gauges are correct,
anyhow. Now we'll try the other two bombs."

In succession they were released from the bottom of the cabin, at other
designated objects. The second one was near a tree. It struck within
five feet, which was considered good.

"And I'll let the last one down near that scarecrow in the field," said
Tom, pointing to a ragged figure in the middle of a patch of corn.

Down went the cardboard bomb, and so good was the aim of the young
inventor that the white dust arose in a cloud directly back of the
scarecrow.

And then a queer thing happened. For the figure seemed to come to life,
and Ned, who was watching through a telescope, saw a very much excited
farmer looking up with an expression of the greatest wonder on his
face. He saw the balloon over his head, and shook his fist at it,
evidently thinking he had had a narrow escape. But the pasteboard bomb
was so light that, had it hit him, he would not have been injured,
though he might have been well dusted.

"Why, that was a man! Bless my pocketbook!" cried Mr. Damon.

"I guess it was," agreed Tom. "I took it for a scarecrow."

"Well, it proved the accuracy of your aim, at any rate," observed
Lieutenant Marbury. "The bomb dropping device of your aerial warship is
perfect--I can testify to that."

"And I'll have the guns fixed soon, so there will be no danger of a
recoil, too," added Tom Swift, with a determined look on his face.