He bent over the boys.  As he had said, Jack’s face was tinged with a light pink, and Mark’s eye-lids were moving slightly.

“They are coming around all right,” exclaimed the aged professor.  “Hurry, Washington, and get some hot beef broth ready.  Put the kettle on to boil and make some strong tea.  They will want something to eat shortly after they recover their senses.”

The colored man, humming softly to himself, began moving about the shed.  It was a rough looking place from the outside, but, within, was fitted with many comforts.  There was a gasoline stove, a table, several chairs, a bed, and a large case full of books.  But the queerest sights of all were on the walls.

They were literally covered with cog wheels, levers, handles, springs, pieces of machinery, patterns, models, and strange devices.  The room had two doors.  One was that by which the old man and the negro had entered.  The other was behind the bed, and was clamped and fastened with so many bolts and bars, with locks similar to those on big safes, that it would seem a rare treasure was concealed behind the portal.

The old man gave no heed to the wonders that surrounded him.  Instead he gave all his attention to the boys.  He sat down beside the bed and watched them as their breathing became stronger.  From time to time he felt of their pulses, and nodded his head as if satisfied.

“Is the beef tea ready?” asked the old man, after a half hour had passed.

“It am, Perfessor.”

“Then turn down the flame a bit so it will keep the stuff warm, and come back into the work shop with me.  I want to get that last bolt in the engine.”

“Are dem young gen’men all hunky-dory?”

“They are coming on nicely,” was the old man’s reply.  “They will recover consciousness in half an hour and we can feed them, and give them some medicine.  Come along, Washington.”

The two passed out through the much-locked door behind the bed, the undoing of the fastenings taking some time.  As the portal swung open it disclosed a long shed which seemed to be occupied with a big, strange object.

The old professor and the negro had not been gone more than five minutes before Jack opened his eyes.  He turned over on one side.  As he did so Mark slowly lifted his head.

“Hello!” cried Jack, faintly.

“What’s the matter?” asked Mark.

“Matter?  What?  Where?” inquired Mark, sitting up.

“Here!  Everywhere!” replied Jack, raising himself slowly on his elbow.  “All I remember is a terrible crash.  Now look at all those wheels.  Wheels!  Wheels!  Wheels!  I wonder if they can be in my head?” and he tried to smile.

“No, they are real wheels, and they are on the walls,” announced Mark.

“Then where in the world are we?” went on Jack.  “In a machine shop or a railroad wreck?”

“Looks like—­” began Mark, when he was interrupted by a voice calling: