“The storage battery!” exclaimed Mark.  “That would give light for a while, if I can only find the switch in the dark.”

He began crawling about on his hands and knees.  It was so intensely black that he ran into many things and received severe bruises.  At last he came to a doorway, and as he did so his hand came in contact with an easy chair.  It was the only one aboard, and by that he knew he had passed into the sitting room.  He had his general direction now, and knew if he kept straight on he would come to the engine room.  There he was familiar enough with the apparatus and levers to be able to turn the electric switch.

Crawling slowly and cautiously, he reached the room where all the engines were.  Then he had to feel around the sides to locate the switch.  At length he found it.  There was a click, a little flash of greenish fire, and the copper conductors came together, and the ship was flooded with the glow from the incandescents.

Mark hurried back to where the others were lying.  They were still unconscious, but an uneasy, movement on the part of Jack told that he was coming out of the stupor.  Mark got some ammonia and held it beneath his comrade’s nose.  The strong fumes completed the work that nature had started and Jack opened his eyes.

“Where am I?  What has happened?  Are any of them dead?” he asked quickly.

“I hope no one is dead,” Mark replied.  “As to the other question, I can’t answer.  I don’t know whether we are a thousand miles underground, or floating on the ocean, though I’m more inclined to the former theory.  But never mind that now.  Help me to bring the others back to their senses.  I’ll work on the professor and you can begin on Bill or Tom.  Washington seems to be all right,” for at that moment the colored man opened his eyes, stared about him and then got up.

“I thought I was dead for suah!” he exclaimed.

“Some of the others may be if we don’t hurry,” said Mark.  “Get to work, Wash!”

With the colored man to help them the two boys, by the use of the ammonia, succeeded in reviving Bill, Tom and old Andy.  But the professor, probably on account of his advanced age, did not respond so readily to the treatment.  The boys were getting quite alarmed, as even some of the diluted ammonia, forced between his lips, did not cause him to open his eyes, or increase his heart action.

“If he should die, and leave us all alone with the ship in this terrible place, what would we do?” asked Jack.

“He’s not going to die!” exclaimed Mark.  “Here I have another plan.  Washington bring that medical electrical battery from the engine room.”  This was a small machine the professor had brought along for experimental purposes.

Quickly adjusting it, Mark placed the handles in the nerveless fingers of Mr. Henderson.  Then he started the current.  In about a minute the eyelids of the aged inventor began to quiver, and, in less than five minutes he had been revived sufficiently to enable him to sit up.  He passed his hand across his forehead.