“Me no drop any, Master,” spoke the giant, as he lifted the boxes of explosives in his strong arms.

The largest gun was loaded and aimed at a distant hill, for Tom knew that if the recoil apparatus would take care of the excess force of his largest gun, the problem of the smaller ones would be easy to solve.

“Here, Rad, where are you going?” Tom asked, as he noticed the colored man walking away, after having completed a task assigned to him.

“Where’s I gwine, Massa Tom?”

“Yes, Rad, that’s what I asked you.”

“I—­I’se gwine t’ feed mah mule, Boomerang,” said the colored man slowly.  “It’s his eatin’ time, jest now, Massa Tom.”

“Nonsense!  It isn’t anywhere near noon yet.”

“Yais, sab, Massa Tom, I knows dat,” said Eradicate, as he carefully edged away from the big gun, “but I’se done changed de eatin’ hours ob dat mule.  He had a little touch ob indigestion de udder day, an’ I’se feedin’ him diff’rent now.  So I guess as how yo’ll hab t’ ’scuse me now, Massa Tom.”

“Oh, well, trot along,” laughed the young inventor.  “I guess we won’t need you.  Is everything all right there, Koku?”

“All right, Master.”

“Now, Ned, if you’ll stand here,” went on Tom, “and note the extreme point to which the hand on the pressure gauge goes, I’ll be obliged to you.  Just jot it down on this pad.”

“Here comes someone,” remarked the bank clerk, as he saw that his pencil was sharpened.  He pointed to the field back of them.

“It’s Mr. Damon,” observed Tom.  “We’ll wait until he arrives.  He’ll be interested in this.”

“Bless my collar button, Tom!  What’s going on?” asked the eccentric man, as he came up.  “Has war been declared?”

“Just practicing,” replied the young inventor.  “Getting ready to put the armament on my aerial warship.”

“Well, as long as I’m behind the guns I’m all right, I suppose?”

“Perfectly,” Tom replied.  “Now then, Ned, I think we’ll fire.”

There was a moment of inspection, to see that nothing had been forgotten, and then the big gun was discharged.  There was a loud report, not as heavy, though, as Ned had expected, but there was no puff of smoke, for Tom was using smokeless powder.  Only a little flash of flame was observed.

“Catch the figure, Ned!” Tom cried.

“I have it!” was the answer.  “Eighty thousand!”

“Good!  And I can build a recoil check that will take up to one hundred and twenty thousand pounds pressure.  That ought to be margin of safety enough.  Now we’ll try another shot.”

The echoes of the first had hardly died away before the second gun was ready for the test.  That, too, was satisfactory, and then the smaller ones were operated.  These were not quite so satisfactory, as the recoil developed was larger, in proportion to their size, than Tom had figured.

“But I can easily put a larger hydrostatic check on them,” he said.  “Now, we’ll fire by batteries, and see what the total is.”