d.
He was at work over a low bench built of a board across two boxes.
So intent was Garwood on what he was doing that he appeared not
to have heard the approach of the boys.

Dick Prescott stood looking on, one hand raised as a signal for
the silence of those behind him. But both Dave and Tom had caught
sight of the stranger at about the same instant.

"If any who know me have hinted that my brain is not strong enough,"
muttered Garwood, whose back was turned to the startled Grammar
School boys, "there is bound to be a great awakening when my wonderful
invention is perfected. Then the world will bow down to me, for
I shall be its master."

"Crazy as a porous plaster!" muttered Tom Reade under his breath.

"It will be a new, a strange sensation," continued Garwood, speaking
just loud enough to be heard by the onlookers. "A great sensation,
too, to be master of the world when, during these present dark
days, I am compelled to run and hide for fear envious scientists
will succeed in capturing me and locking me up."

"I wonder what he thinks he's doing there?" pondered Dick curiously.

"To think that a few grains of this wonderful substance would
pulverize a regiment!" continued Garwood, in an inventor's ecstasy.
"An ounce of this wonderful material enough to blow up an army
corps. A single pound sufficient to bring the nations of the
world to my feet in awed homage. And I can make a hundred pounds
a day of it! Oh, that I could reach other worlds, to make them
feel my mastery!"

"If his stuff is as good as he thinks it is, I certainly hope
he won't shoot off any of it accidentally," thought Prescott,
with an odd little shiver.

"Oh, that I dared trust my secret to one or two others!" murmured
Garwood, as he delved with one hand into one of the boxes that
supported his simple bench. "And now for the great finishing
touch!"

Amos Garwood placed on the board a fairsized wide-mouthed bottle.
From where he stood, Dick could read the label on the bottle---
"Potassium Chlorate---crystals."

"Chlorate of potash?" thought Dick. "That's what Dr. Bentley
gave me once for sore throat."

Dick, however, was soon to get an inkling of a suspicion that
chlorate of potash might be used to serve other purposes.

As the mentally queer inventor reached into the box for that bottle,
the three silent, observing "Injuns" saw that Garwood had on the
crude table before him a glass mortar and pestle, the former of
about two quarts'