A ?. As scat or puerile as is may seem, whenever I view a pic of the clippers in port, with heads over or near dock, I wonder, "where did they go," meaning with the head so present, where did the crew go potty?
That's about the only explicit detail NOT much addressed in Two Years Before the Mast - which should be required reading in US schools, but I wonder what grade is appropriate? Of course, they'd edit out the captain going apeshit and flogging the crewmember...but as a first-person historical account it's hard to beat from an American perspective.
Since those ships mostly ran before the wind, I kind of doubt the stern rail was a good place, particularly as the captain and first mate had their cabins there with windows open during fair weather to let air in. I actually heard the term head originated from using the safety netting between the bow and sprit as the place top have a go. Don't know if that's true but I read it in a fictional work somewhere.
The head(aft of the figurehead) was actually the place where the crew did the dirty when at sea in a following wind and sea as Kindardly correctly states. The poop deck, French for Le puope’, was the raised aft deck so the Captain and ship’s pilot could see over the fore decks, etc.
Funny that the title of Dana's book "Two years before the mast" didn't give you a clue. Seamen were not allowed aft, especially the aft deck, while at sea, unless by invitation from an officer. A turn at the helm was given only to a few men.
Would have been considered mutiny for a sailor to stroll to the officer's deck. Lashings would be issued.
The sailors were confined to the forward decks.
The poop deck, according to wikipedia, refers to the french le poupe, latin: puppis. From the argonauts, was the name of one of three constellations that made up the night sky. Was used for navigation in ancient times. In other words, the observation deck. Modern ships now perform this at the bridge.