[cherokee1]

Sounds like a porthole to me----there's a whole bunch of good reasons that subs don't have ém. But God bless the old timers for trying. Altho this isn't yet identified as the reason the Hunley went down it would have been sooner or later. ---another reason we say the Navy ship design book is written , page by page, in blood.

[Bogey78O]

Wonder if the glass broke and the seal didn't function.

[Doctor Stochastic]

Good design is a result of experience.
Experierce is a result of bad designs.

[TalonDJ]

I disagree that it was a bad feature. This ship had to use lamps under water. I.E. fire and some smoke. When running near or on the surface these windows would have allowed them to run without burning things inside. Modern battle subs don't have port holes but bathyscapes do and they go deeper. On a battle sub they are pointless since there are electric lights and not a usable amount of light at periscope depth.