“Here! Stop him!” cried Professor Henderson. “Don’t let him get away. We still need his help to get the ship in shape. He needn’t be frightened. We’re not going to start at once.”
Mark and Jack1 ran after Washington, whose progress was somewhat impeded2 because he kept looking back as if he feared the new ship was chasing him.
“Come on back!” said Mark. “There’s no danger, and if there was we’re not going to start to-day.”
“Ain’t yo’ foolin’ me?” asked Washington, pausing and looking doubtfully at the boys.
“Of course not,” answered Mark. “You know Professor Henderson would not make you do anything you didn’t want to do, Wash. He wishes you to stay and help him get ready, that’s all.”
“Well, Washington,” observed the aged3 scientist. “I didn’t think you’d go back on me.”
“I’d do mos’ anything fer yo’, Perfesser,” said the colored man, “but I got t’ beg off this time,” and he looked at the Flying Mermaid4 as if he thought the metal sides would open and devour5 him.
“Then help me get things in shape to generate the gas,” the scientist said. “I want to give the new vapor6 the first real test in lifting power to-day. On the success of it depends the future of the ship.”
Seeing there was no immediate7 danger of being carried to the centre of the earth, Washington resumed his labors8. The professor, the boys, Bill and Tom were also hurrying matters to enable a test to be made before night.
As will readily be seen, even by those not familiar with the construction of airships and submarines, the chief problem was to find some agent strong enough to lift from the earth a weight heavier than had ever before been put into an apparatus9 that was destined10 to traverse the clouds. For the Flying Mermaid was not only an airship but an ocean voyager as well. It had to be made light enough to be lifted far above the earth, yet the very nature of it, necessitating11 it being made heavy enough to stand the buffeting12 of the waves and the pressure of water, was against its flying abilities.
Professor Henderson realized this and knew that the chief concern would be to discover a gas or vapor with five times the lifting power of hydrogen, one of the lightest gases known, and one sometimes used to inflate13 balloons.
After long study he had been partially14 successful, but he knew from experiments made that the gas he had so far been able to manufacture would not answer. What he wanted was some element that could be mixed with the gas, to neutralize15 the attraction of gravitation, or downward pull of the earth.
While he was seeking this, and experimenting on many lines, the construction of the air-water ship went on. In general the outward construction was two cigar shaped hulls17, one above the other. Aluminum18, being the lightest and strongest metal that could be used for the purpose, formed the main part of both bodies.
The upper hull16 was one hundred feet long and twenty feet in diameter at the widest part. It tapered19 to points at either end. It was attached to the lower hull by strong braces20, at either end, while from the center there extended a pipe which connected with the lower section. This pipe was intended to convey the lifting gas to the part which corresponded to the bag of the balloon, save that it was of metal instead of silk, or rubber as is usual.
There were two reasons for this. One was that it would not be liable to puncture21, particularly in the proposed underground trip, and the other was that it did not have to be so large as a cloth bag would have had to be. It was also a permanent part of the ship, and on a voyage where part of the time the travelers would be in the air and part on the water, and when the change from one to the other would have to be made quickly, this was necessary. It would have taken too long to raise the ship in the air had a cloth bag been used to contain the gas.
The lower hull or main part of the craft was one hundred and fifty feet long, and forty feet through at the largest part, in the centre.
It was divided into four sections. The forward one contained the sleeping quarters of Professor Henderson and his crew. There was a small stateroom for each one. Above was a conning22 or observation tower, reached by a small flight of steps. From this tower the ship could be steered23, stopped and started, as could also be done from the engine room, which was in the after part of the hull.
As in the Porpoise24 and Monarch25, electricity formed the motive26 power and was also used for many other purposes on board. Engines operated by gas produced the current which heated, lighted and moved the ship, as well as played a part in producing the wonderful gas.
The ship moved forward or backward by means of a novel arrangement. This was by the power of compressed air. From either end of the lower hull there projected a short pipe working in a ball and socket27 joint28, so it could be turned in any direction. By means of strong pumps a current of compressed air could be sent out ............