[supercat]

From what I read, the Hunley used a candle both as a light source and an oxygen indicator. By my understanding, though, CO2 concentrations in an enclosed space would reach toxic levels long before there was insufficient oxygen to support a candle flame.

My guess as to why the Hunley sank has long been CO2 poisoning.

[Richard Kimball]

I agree. Nobody understood the issues involved in providing breathing air underwater back then. The History Channel had a great show on the Brooklyn Bridge a while back, and how many of the workers developed the bends from working in bells at the bottom of the river.

[TXnMA]

By my understanding, though, CO2 concentrations in an enclosed space would reach toxic levels long before there was insufficient oxygen to support a candle flame.

Dead wrong. During a test of how long the Hunley could stay down with the crew breathing only the enclosed oxygen, the candle went out long before the crew gave up and surfaced. They stayed down two hours (on the bottom, at rest, of course) and the sentry who was waiting for them on shore, gave up and left, thinking that they had perished in the attempt.

FWIW, the Hunley had a rudimentary snorkel system, and one of the crew was assigned to work the bellows, rather than to crank the propeller.

I'm surprised that there is any claim to mystery about the opened hatch. The snorkel worked only on the surface, and was one way only. In order to get effective air exchange, a hatch had to be opened. Besides, sentries on Sullivan's Island reported that Dixon signaled to shore with his blue-lensed carbide lantern. That act would have entailed opening his hatch, as well.

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FYI, I conducted preliminary studies on the Hunley in prep for its raising. It was my company's on-line forum of engineers and historians who (accurately) predicted that the torpedo boom or "spar" was a metal pipe, 18-20 feet long, and was deployed from the bottom of the bow at a downward angle of 30 degrees, This was based on the fact that the Hunley (following Gen. Beauregard's orders) attacked on the surface -- yet the explosion severed the Housatonic's propeller shaft.

It was shortly following our 30-degree downward angle prediction, that Hunley historian, Mark Ragan, posted the following sketch to our forum:

(Note the 30-degree angle of the spar socket...)

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I am not surprised the hatch was opened -- but I still can't help but wonder if the missing forward "deadlight" in the front hatch tower also could have played a role in the combat loss of the world's first successful attack submarine...

[75thOVI]

I wrote that suggestion up as a monograph and submitted it to the Hunley museum. I suggested that the small medicine bottle found in the sub was to help mitigate the effects of CO2 poisoning. (Cracking headache.) A couple of years a go I was able to visit the Hunley, and asked what they thought about the theory. The docent I talked to said it was "just about on a par with Kidnapped By Aliens." Oh well, I'll stick with the CO2 theory anyway.