“I reckon I was brought up t’ it,” replied the colored man grinning from ear to ear. He did not always use big words but when he did they were generally the wrong ones. Sometimes, he spoke quite correctly. “Well, I suppose you can’t help it,” resumed Mr. Henderson. “However, never mind that. Find the boys and send them to me.” “With th’ least appreciatableness amount of postponement,” answered the messenger, and he went out. Washington White, who in color was just the opposite to his name, a general helper and companion to Professor Henderson, found Mark Sampson and Jack Darrow about a quarter of a mile from the big shed, which was in the center of a wooded island off the coast of Maine. The lads were seated on the bank of a small brook, fishing. “Perfesser wants yo’ immediate,” said Washington. “But we haven’t caught a single fish,” objected Mark. “Them’s the orders from headquarters,” replied the colored man. “Yo’ both got t’ project yo’selves in th’ vicinity of th’ machine shop. I reckon th’ new fangled contraption that th’ perfesser is goin’ t’ navigate th’ air an’ sail th’ angry seas in, am about done. He want’s t’ try th’ engine.” “Come on then,” said Jack. “We probably would not catch any fish, anyhow, Mark.” Accompanied by Washington, the youths, each of whom was about eighteen years old, started toward the big shed. While they are on their way opportunity may be taken to tell a little about them, as well as about Washington and the professor, and the curious craft on which the scientist was working. A few years before this story opens Mr. Henderson had invented a wonderful electric airship. He had it about completed when, one day, he and the two boys became unexpectedly acquainted, and, as it developed, friends. Mark and Jack were orphans. After having rather a hard time knocking about the world trying to make a living, they chanced to meet, and resolved to cast their lots together. They boarded a freight train, and, as told in the first volume of this series, entitled, “Through the Air to the North Pole; or the Wonderful Cruise of the Electric Monarch,” the cars were wrecked near where Professor Henderson was building his strange craft. The boys were cared for by the scientist, and, after their recovery from hurts received in the collision, they accepted his invitation to make the trip through the upper regions in the airship, to search for the north pole. With them went Andy Sudds, an old hunter, and Tom Smith and Bill Jones, two farmers, but who were hired as helpers on the voyage. The party had many adventures on the trip, having battles with savage animals and more savage Esquimaux, and were tossed about in terrible storms. After making some scientific observations, which the professor was much interested in, they started back home. Having found he could successfully sail in the air, Mr. Henderson resolved to try what it might be like under water.