n."

"Sit on a cannon, Massa Tom! Say, looky heah now! You jest take dese
primary things from dish yeah coon. I--I'se got t' go!"

"Why, what's the matter, Rad? Surely you're not afraid; are you?" and
Tom winked at Ned.

"No, Massa Tom, I'se not prezactly 'skeered, but I done jest 'membered
dat I didn't gib mah mule Boomerang any oats t'day, an' he's suahly
gwine t' be desprit mad at me fo' forgettin' dat. I--I'd better go!"

"Nonsense, Rad! I was only fooling. You can go as soon as we get to my
private proving grounds, if you like. But you'll have to carry those
primers, for all the rest of us have our hands full. Only be careful of
'em!"

"I--I will, Massa Tom."

They kept on, and it was noticed that Mr. Damon gave nervous glances
from time to time in the direction of Koku, who was carrying the box of
powder. The giant himself, however, did not seem to know the meaning of
fear. He carried the box, which contained enough explosive to blow them
all into fragments, with as much composure as though it contained
loaves of bread.

"Now you can go, Rad," announced Tom, when they reached the lonely
field where, pointing toward a big hill, was the little cannon.

"Good, Massa Tom!" cried the colored man, and from the way in which he
hurried off no one would ever suspect him of having rheumatic joints.

"Say, that stuff looks just like Swiss cheese," remarked Ned, as Tom
opened the box of explosive. It would be incorrect to call it powder,
for it had no more the appearance of gunpowder, or any other "powder,"
than, as Ned said, swiss cheese.

And, indeed, the powerful stuff bore a decided resemblance to that
peculiar product of the dairy. It was in thin sheets, with holes
pierced through it here and there, irregularly.

"The idea is," Tom explained, "to make a quick-burning explosive. I
want the concussion to be scattered through it all at once. It is set
off by concussion, you see," he went on. "A sort of cartridge is buried
in the middle of it, after it has been inserted in the cannon breech.
The cartridge is exploded by a primer, which responds to an electric
current. The thin plates, with holes corresponding to the centre hole
in a big grain of the hexagonal powder, will, I hope, cause the stuff
to burn quickly, and give a tremendous pressure. Now we'll put some in
the steel tube, and see what happens."

Even Tom was a little nervous as he prepared for this latest test. But
he was not nervous enough to drop a