Lock

Lock, on a river or canal, is an arrangement of two parallel floodgates, by which communication is secured between two reaches of different levels. Without locks, canals are an impossibility in any but exceptionally level country. The principle of locks is explained in the article CANAL, Vol. II. p. 697. The invention of the lock has been claimed for the great Leonardo da Vinci or other Italian engineer of the 15th century; but there seems ground for affirming that the principle was known and used in Holland a hundred years earlier.