on went over to the bed on which the two boys were stretched
out, each with the piece of cotton soaked in the preparation over his
mouth and nose.

"I am using a very powerful remedy," the old man muttered. "If they are
not too badly hurt they will recover. Ah, yes, there is a little color
in their pale cheeks."

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