CHAPTER II

 The flying Mermaid

“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 Jack ran after Washington, whose progress was somewhat impeded 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 aged 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 Mermaid as if he thought the metal sides would open and devour him.

Then help me get things in shape to generate the gas,” the scientist said.  “I want to give the new vapor the first real test in lifting power to-day.  On the success of it depends the future of the ship.”

Seeing there was no immediate danger of being carried to the centre of the earth, Washington resumed his labors.  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 apparatus that was destined 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, necessitating it being made heavy enough to stand the buffeting 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 inflate balloons.

After long study he had been partially 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 neutralize 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 hulls, one above the other.  Aluminum, being the lightest and strongest metal that could be used for the purpose, formed the main part of both bodies.