"I haven't said much to you about my plans," the professor replied, "but if you would like to remain in my employ, I can promise you an interesting trip."

"Thank you, but I prefer to work above ground," said James Pensen. "You have been very kind to us, and we would do anything we could for, but we don't want to take any long under-ocean trips if we can help it."

"Very well," answered the professor, though he seemed disappointed. "I will pay you what I owe you and you can go."

For some time after the departure of the two young machinists the inventor seemed worried.

"Did you count on them staying with you?" asked Mark.

"I rather hoped they would," replied Mr. Henderson. "We need two more hands if we are to make the trip. They need not be machinists, but we will have to have someone, and I don't like to get strangers. They might talk too much about the ship."

At that instant there came a rap on the door. Washington answered it.

"Yas sir, Perfesser Henderson done lib here," he replied, in answer to a question from some one. "But he am bery busy jest at de present occasioness an' he'll be most extremely discommodated if yo' obtrude yo'

presence on him at de conglomeration ob de statutory limitations, which am to say right now. Come again!"

"It's the same old Washington!" said someone outside, laughing heartily.

"Just you tell the professor we want to see him most particular."

At the sound of the voice the professor started and Mark and Jack wondered where they had heard it before.

"Show the gentlemen in, Washington," called the inventor.

"Dere's two ob 'em," objected the colored man.

"Show them both in, then."

Washington opened the door of the cabin, and in came two men, who seemed much amused over something.

"What can I do for you?" asked the professor, in rather a sharp voice.

"He don't know us either, Tom," remarked the taller of the two.

"If it ain't Bill Jones and Tom Smith!" exclaimed Andy Sudds. "Wa'al I'll be horn swoggled. Where'd ye come from?"

"Right from the farm," replied Bill. "And we've had a hard job locating you. I guess Washington didn't know us since we raised beards," and Bill stroked his wealth of brown whiskers.

"And I guess we sort of fooled the professor," went on Bill, "eh, Tom?"

"Right!" said Tom. "You see," he went on, "the farming business is almost over, as its coming on fall now, so Bill and I thought it would be a good time to hunt up the professor. We heard he was down in this neighborhood so we come by easy stages. We didn't have any time to stop and make our toilets, hence our beards."

"You've come at the right time," remarked the inventor, as he came forward to welcome the two young men. "Do you remember the trip you made with me to the north pole?"

"I guess we'll not forget it in a hurry," replied Bill.

"That's what made us hunt you up," put in Tom. "We hoped you might have something similar on foot."

"I have," answered the inventor.

"What is it?"

"A trip under the ocean!"

For an instant the two young men hesitated. It was a new proposition to them. Yet they recalled that they had come safely back from the journey through the air.

"Do you want to go along as part of the crew?" asked the inventor, after some further conversation.

"You can count on me!" cried Bill.

"And if Bill goes I'll go too!" exclaimed Tom.

"Under the seas or over the seas, it'll be all one to us if Professor Henderson sails the ship!" went on Bill. "We'll go!"

"Good!" e.j.a.c.u.l.a.t.ed the professor. "You certainly came at just the right time."

As Tom Smith and Bill Jones were hungry a hasty meal was prepared for them, during the eating of which they told of their experiences since landing from the airship. They had been on a farm until fired with a desire to go roving once more.

For the next few days the professor, the boys, and the other four were busy making some improvements to the _Porpoise_. Tom and Bill were much astonished at their first sight of the queer craft, but they soon became accustomed to her, and said they preferred her to the airship.

"To-morrow we are going on a little longer trip than our first trial,"

announced the inventor one evening. "We will be gone all day if nothing happens to make the stay more lengthy," he added grimly. "So, Washington, put plenty to eat aboard."

A little later, when supplies had been put on the _Porpoise_, and the machinery well overhauled, the professor explained that he intended making a trip, entirely under water, from the dock in the cove to a point off the Ma.s.sachusetts coast and return.

Early the next morning all were aboard. To each one was a.s.signed a particular station. Washington, with Mark as an a.s.sistant, was in the engine-room. Jack was to watch the various gages and registers to give warning of any danger. The professor, of course, would be in the conning tower and operate the craft. Andy was to be with him, to watch out, with his sharp eyes, for any danger that might loom up in the path of the searchlight. Tom and Bill were to be ready to help where needed.

With a hissing sound the water filled the tanks and the _Porpoise_ sunk beneath the waves. The engine that worked the endless screw was started, and the threads, working on the water cable, shot the boat ahead.

"We're off!" yelled Washington.

About sixty feet below the surface the craft was sent along. Mile after mile was covered as shown by the patent log. The lights were turned off, and through the thick plate gla.s.s windows the strange inhabitants of the sea were observed.

"I think I'll go a little nearer the surface," said the professor to Andy. The inventor started the pumps that emptied the tanks. The craft rose slightly.

"Quick! Stop her!" shouted the old hunter, grasping the captain's arm.

Something black, like a grim shadow, loomed up in the dull glare of the searchlight.

"What is it?" cried the professor.

"We're goin' to hit somethin' hard!" yelled Andy.

"It's the hull of a ship!" exclaimed the inventor as he jammed the reversing lever hard over.

It was too late. The next instant the _Porpoise_, with a shock that made her shiver from stem to stern, collided with the steel side of a small warship.