ChronotechAn atlas of how we made the world

Transportation · Vol. VII|Canal lock|984 (Pound lock, China); later Europe

Canal lock

984 (Pound lock, China); later Europe

A river runs downhill. A canal wants to be level. A lock is a water elevator: a chamber with gates that can be filled or emptied so a boat rises or falls without a portage. The pound lock recorded in 10th-century China, and later European systems, turned inland water into a controlled road. Bulk cargo could climb a landscape.

Qiao Weiyue (recorded pound lock on the Grand Canal) · China; later Low Countries and Britain

Canal lock — Original plate drawn for this atlas. Not a photograph of a museum object or a copyrighted portrait.

How the mechanism is arranged

A pound lock is a water elevator: fill the chamber to raise a boat, empty it to lower one.

How it works

Float the boat into a chamber and close the downhill gate.
Let water in (or out) until the boat sits at the next level.
Open the uphill gate and proceed.

Why it mattered

Linked watersheds that nature had separated.
Cut the cost of grain, coal, and stone before railways.
Showed that infrastructure could rewrite geography.

Who turned the wheel

1136–1206Ismail al-Jazari

What it unlocked

For further study

Needham, Science and Civilisation in China. Grand Canal locks.
Hadfield, World Canals. Comparative lock history.

Check

What does a lock spend in order to lift a boat?