"That's all."

"Oh, if it's only a theory, den I reckons it's all right," came from
the colored man. "I didn't know it were a theory. Dat makes it all
right. It's jest in theory, am it, Massa Mark, dat a stone goes six
times as far?"

"That's all."

"Oh, well, den, why didn't yo' say so fust, dat it was only a theory? I
don't mind theories. I--I used t' eat 'em boiled an' roasted befo' de
wah." And, with a contented smile on his face, Washington went into the
projectile, to finish stowing things away in his kitchen lockers.

The big projectile was housed in the shed where it had been
constructed, and the professor and the boys were working over it there,
carefully guarded from curious eyes, for the German inventor did not
want the secret of his Cardite motor to become known.

The work went on from day to day, good progress being made. The boys
were of great assistance, for they were practical mechanics, and had
had considerable experience.

"Well, I shall try the Cardite motor to-morrow," announced Professor
Roumann one night, after a hard day's work on the projectile.

"Do you think it will work?" asked Mr. Henderson.

"I think so, yes. My experiments have made me hopeful."