Late in the morning we were awakened by the Rebel patrol and taken back to the prison.

Lieutenant Davis, disgusted with the perpetual attempts to escape, moved the Dead Line out forty feet from the Stockade; but this restricted our room greatly, since the number of prisoners in the pen had now risen to about six thousand, and, besides, it offered little additional protection against tunneling.
It was not much more difficult to dig fifty feet than it had been to dig thirty feet.

Davis soon realized this, and put the Dead Line back to twenty feet.

His next device was a much more sensible one.

A crowd of one hundred and fifty negros dug a trench twenty feet wide and five feet deep around the whole prison on the outside, and this ditch was filled with water from the City Water Works.