A junk under repair in dry dock in Hong Kong. Four or five transverse bulkheads can be seen inside the ship. In addition, five ribs or frames are visible. The habit of building hulls like this meant that watertight compartments were possible. If a leak occurred in one section, it could be sealed off from the rest and the ship remained afloat. Chinese ships had watertight compartments from at least the second century AD, but the idea only caught on in the West at the end of the eighteenth century. (Waters Collection, National Maritime Museum, London.)

From The Genius of China by Robert Temple