page forty-six

The Lock

Forty-five rooms, and nothing in any of them ever had to wait its turn. Today's number cuts a canal over a hill, climbs it by a flight of locks and puts you at the top with the windlass. Boats come up and boats come down. Every lockful you draw comes out of a summit the company is watching, and every minute you hold a boat back is a minute her horse stands in the rain.

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The flight, from the bottom pound up to the summit
At the foot, going up
At the head, coming down
The lock-keeper's book
Lock
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The arrow keys walk to other days. Every day is a different canal, a different flight and a different set of boats.

What is real here and what is not

The way a lock spends water, the fly-boats and the keeper's problem are real. The canals, the boats and the timings are the day's number and a simplification.

  1. 01

    Water is the whole budget

    A canal that crosses a hill has to be fed at the top, from reservoirs and feeders, and every boat that crosses the summit lets water run down both sides. Through the dry summers of the canal age, companies counted their summit in inches, posted gauges, chained up flights at night and fined boatmen for drawing a lock that did not need drawing. A narrow lock of seven or eight feet takes something like twenty-five thousand gallons at a go.

  2. 02

    Why the order matters

    A boat going up has to fill the top lock from the summit, so every upward boat costs a lockful. A boat coming down needs the locks full: if the last boat went up and left them so, she comes down on that water for nothing; if the last boat went down, the flight is empty and has to be filled for her from the summit first. Working boats up and down alternately halves the water and saves the time of setting the locks. Waiting for a boat coming the other way keeps somebody waiting, and that is the whole game.

  3. 03

    Fly-boats

    Most boats carried coal, lime, stone and bricks at walking pace and nobody minded an hour. Fly-boats carried parcels and general goods to a timetable, worked day and night with relays of horses and fresh crews, and were given the right of way at locks. Keep one waiting and the carrier hears of it.

  4. 04

    How the old keeper's book is found

    The book is an exact search, not a rule of thumb. For every set of boats already through and each way the flight could have been left, the page keeps only the part-days that nothing else beats at once on the clock, the water drawn and the boat-minutes waited, and extends each by every boat still to come. The water allowance is set between the least water any order can manage and what working the boats strictly as they come would draw, so first come, first served will not do.

Forty-six rooms, and one number doing all the work. Today it cuts a canal over a hill, fills the summit and sends the boats to the flight in an order nobody chose.