any disproportionable
anticipation ob transposin' dem molecules of lead in a contigious
direction to yo' humble servant!" exclaimed a colored man, coming from
behind the big shed at that moment, and seeing Mark and Jack with their
rifles.

"I s'pose you mean to say, Washington," remarked Jack, "that you don't
care to be shot at. Is that it?"

"Neber said nuffin truer in all yo' born days!" exclaimed Washington
earnestly. "De infliction ob distress to de exterior portion ob--"

"The professor wants you," interrupted Mark, cutting off the colored
man's flow of language.

"Yo' mind what I tole yo'," Washington muttered as he hurried into the
work room.

Soon the reports of rifles indicated that the boys were trying to
discover who was the best shot, a contest that waged with friendly
interest for some time.

The big shed, where the submarine ship was being built, was located at a
lonely spot on the coast of Maine. The nearest town was Easton, about
ten miles away, and Professor Henderson had fixed on this location as
one best suited to give him a chance to work secretly and unobserved on
his wonderful invention.

The professor was a man about sixty-five years old, and, while of simple
and kindly nature in many ways, yet, on the subjects of airships and
submarines, he possessed a fund of knowledge. He was somewhat queer, as
many persons may be who devote all their thoughts to one object, yet he
was a man of fine character.

Some time before this story opens he had invented an electric airship in
which he, with Mark Sampson, Jack Darrow and the colored man,
Washington White, had made a trip to the frozen north.

Their adventures on that journey are told of in the first volume of this
series, entitled, "Through the Air to the North Pole, or, The Wonderful
Cruise of the _Electric Monarch_."

The two boys, Mark then being fifteen and Jack a year older, had met the
professor under peculiar circumstances. They were orphans, and, after
knocking about the world a bit, had chanced to meet each other. They
agreed to seek together such fortune as might chance to come to them.

While in the town of Freeport, N. Y., they were driven away by a
constable, who said tramps were not allowed in the village. The boys
jumped on a freight train, which broke in two and ran away down the
mountain, and the lads were knocked senseless in the wreck that
followed.

As it chanced Professor Henderson had erected nearby a big shop, where