One of the first things that struck me as I viewed Fort Jefferson's walls was this phenomenon: Giant, untidily gaping holes where the fort's second-tier firing embrasures should be. Was some angry god jealous of the ingenious innovation of Totten Shutters, and slaked his fury by individually (and somewhat surgically) bashing in each embrasure?

Nope. Fort Jefferson was never completed. Construction slowed with the outbreak of the Civil War, in that it was being built with bricks from Florida, which proved to be less than cooperative with (and less than willing to provide bricks to) the Federal Government upon its secession in January of 1861. Construction continued at a diminished pace after the war, and the fort remained unfinished when the garrison left in 1874, following a deadly outbreak of Yellow Fever and bad storm. Thus, Fort Jefferson's second-tier embrasures were never installed.