Bulkhead
2 of the 7 encyclopedias on this shelf carry an entry for Bulkhead. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a partition in the hull of a ship. The portion of a ship below the waterline is divided into compartments, usually by water-tight partitions running crosswise and lengthwise. In case a hole is made by running against a rock or by some other accident, the water-tight doors in the partitions surrounding the space through which water is entering are closed tightly, and, though the room may fill with water, the ship suffers little inconvenience. No charge of grosser neglect can be brought against a ship's commander than one of neglecting to close his bulkheads in case of collision at sea. As the front end of a ship is most apt to be stove in, the forward bulkhead is made with especial care and is called the collision bulkhead. The term is applied also to any framework designed to prevent water or quicksand from breaking into a tunnel while the workmen are at work. 2026 Editor's Note: This confident passage was published almost exactly as its argument was disproved. The Titanic sank in April 1912 despite sixteen watertight compartments, because her bulkheads did not reach high enough: as the bow went down, water simply spilled over the tops from one compartment into the next. The disaster rewrote ship safety rules worldwide. (Ed: BR 2026-07-06)
Collier's New Encyclopedia (1921)
a partition made across a ship, whereby one part is divided from another; also, a wood or stone construction designed to prevent earth or water from falling or flowing into the space protected by a bulkhead. A bulkhead line is a line a given distance from the shore, beyond which it is not permissible to build a dock, according to the rules of the War Department at Washington.