This tower is obviously part of some later remodeling and expansion that occurred long after the initial construction.
There was a legendary escape from here where inmates tunneled down and under the wall from a cell. One of the escapees
was bank robber Willie Sutton who apparently took undeserved credit for the episode even though he neither originated
nor worked on the project. (He was the first caught -- in 15 minutes -- because he was so recognizable!)