X. To sea, and the end of the line

At sea the compound’s argument is made a third time: the marine triple-expansion engine spends its steam through three cylinders and two floating receivers, on three cranks set a third of a turn apart — so some cylinder is always at full push, and the engine needs no flywheel, no barring over, and, strangest of all, no governor: a propeller’s resistance grows as the square of its speed and holds the engine steady by itself. Drag the load below and watch the speed obey the water. This is the engine that drove the liners — the Titanic carried two, four storeys tall, beside a turbine that drank their exhaust. And that turbine is the end of our story: within a decade it took the engine room whole, and the beautiful machinery of pistons and cranks became a museum — this one. Each tab above is one of these chapters made iron; the question-marks beside every lever will remind you of the rest.

One chapter of nine. Read the whole Primer, or work the engines themselves.