"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 he was building his airship. He and Washington were on hand when the wreck occurred and they took the senseless boys to the airship shed.
The boys, after their recovery, accepted the invitation of the professor to go on a search for the north pole. As the airship was about to start Andy Sudds, an old hunter, and two men, Tom Smith and Bill Jones, who had been called in to assist at the flight, held on too long and were carried aloft.