repeated his cries until be was weary. No one answered him.
He fancied once he could hear footsteps in the shed, and
thought, perhaps, it was Andy, come back to gloat over him.
Then Tom knew the red-haired coward would not dare venture
back. We must do Andy the justice to say that he never
realized that he was endangering Tom's life. The bully had
no idea the tank was airtight when he closed it. He had seen
Tom enter and a sudden whim came to him to revenge himself.

But that did not help the young inventor any. There was no
doubt about it now--the air was becoming close. Tom had been
imprisoned nearly two hours, and as he was a healthy, strong
lad, he required plenty of oxygen. There was certainly less
than there had been in the tank. His head began to buzz, and
there was a ringing in his ears.

Once more he fell upon his knees, and his fingers sought
the small projections of the gear on the inside of the door
He could no more budge the mechanism than a child could open
a burglar-proof vault.

"It's no use," he moaned, and he sprawled at full length
on the floor of the tank, for there the air was purer. As he
did so his fingers touched something. He started as they
closed around the handle of a big monkey wrench. It was one
he had brought into the place with him. Imbued with new hope
be struck a match and lighted his lantern, which he had
allowed to go out as it burned up too much of the oxygen. By
the gleam of it he looked to see if there were any bolts or
nuts he could loosen with the wrench, in order to slide the