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 any of those queer, cheese-like slabs. For, though he knew that a considerable percussion was needed to set them off, it would not do to take chances. High explosives do not always act alike, even under the same given conditions. What might with perfect safety be done at one time, could not be repeated at another. Tom knew this, and was very careful.
The powder, as I shall occasionally call it for the sake of convenience, though it was not such in the strict sense of the word—the powder was put in the small cannon, together with the primer. Then the wires were attached to it, and extended off for some distance.
"But we won't attach the battery until the last moment," Tom said. "I don't want a premature explosion."
The projectile was also put in, and Tom once more looked to see that the armor plate was in place. Then he adjusted the various gauges to get readings of the power and energy created by his new explosive.