Sentence:  I waited until half an hour after Benson had gone on duty, and then I went on deck, passing through the <WSD>conning-tower</WSD> where Benson sat, and looking at the compass. It showed that our course was north by west--that is, one point west of north, which was, for our assumed position, about right. 
Meaning of the word marked with <WSD> tags:  A connecting structure between the bridge and pressure hull of a submarine; in larger, modern submarines it contains the captain's cabin and is known as the sail.