later, when they
were again back in the office, the excitement having calmed down. The
expressman had gone back to town afoot, to arrange about getting
another vehicle for what remained of his load. "Is it the kind they use
in big guns?"

"One of the kinds," replied Tom. "I sent for several samples, and this
is one. I'm going to conduct some tests to see what kind I'll need for
my own big gun. But I expect I'll have to invent an explosive as well
as a cannon, for I want the most powerful I can get. Want to look at
some of this powder?"

"Yes, if you think it's safe."

"Oh, it's safe enough if you treat it right. I'll show you," and
working carefully Tom soon had one of the boxes open. Reaching into
the depths he held up a handful of something that looked like sticks of
macaroni. "There it is," he said.

"That powder?" cried Ned. "That's a queer kind. I've seen the kind they
use in some guns on the battleships. That powder was in hexagonal form,
about two inches across, and had a hole in the centre. It was colored
brown."

"Well, powder is made in many forms," explained Tom. "A person who has
only seen black gunpowder, with its little grains, would not believe
that this was one grain of the new powder."

"That macaroni stick a grain of powder?" cried Ned.

"Yes, we'll call it a grain," went on the young inventor, "just as the
brown, hexagonal cube you saw was a grain. You see, Ned, the idea is to
explode all the powder at once--to get instantaneous action. It must
all burn up at once as soon as it is detonated, or set off.

"To do that you have to have every grain acted on at the same moment,
and that could not be done if the powder was in one solid chunk, or
closely packed. For that reason they make it in different shapes, so it
will lie loose in the firing chamber, just as a lot of jack-straws are
piled up. In fact, some of the new powder looks like jack-straws. Some,
as this, for instance, looks like macaroni. Other is in cubes, and some
in long strings."

As he spoke Tom struck a match and held the flames near the end of one
of the "macaroni" sticks.

"Caesar's grandmother!" yelled Ned. "Are you crazy, Tom?" as he started
to leap for a window.

"Don't get excited," spoke Tom, quietly. "There's no danger," and he
actually set fire to the stick of queer powder, which burned like some
wax taper.

"But--but--" stammered Ned.

"It is only when powder is confined that it explodes," Tom explained.
"If it