"A capital instrument for my purpose," thought Jack, shouldering it, "and worth all the trouble I have had in procuring it." While he was thus musing, he fancied he heard the lock tried.

A chill ran through his frame, and, grasping the heavy weapon with which chance had provided him, prepared to strike down the first person who should enter the cell.

After listening attentively for a short time without drawing breath, he became convinced that his apprehensions were groundless, and, greatly relieved, sat down upon the chair to rest himself and prepare for further efforts.
Acquainted with every part of the jail, Jack well knew that his only chance of effecting an escape must be by the roof.

To reach it would be a most difficult undertaking.

Still it was possible, and the difficulty was only a fresh incitement.
The mere enumeration of the obstacles that existed would have deterred any spirit less daring than Sheppard's from even hazarding the attempt.
Independently of other risks, and of the chance of breaking his neck in the descent, he was aware that to reach the leads he should have to break open six of the strongest doors of the prison.