Define: STOP LOCK
A stop lock is simply a lock between two canals that are very close to each other in water level.
Two centuries or more ago, when one canal was built to join up to another, existing, canal, it was difficult to get the two stretches to match exactly in water level. Wiithout a stop lock between, then the canal with the higher water level would naturally - and quickly - lose its water. And since the two canals would (usually) be separate businesses - and water was the very stock in trade of canal companies - the water loss would represent a commercial loss.
So a stop lock would allow the canal companies to control and 'meter' how much water was lost to their competitor.
Perhaps the most picturesque is Hawkesbury Junction at the junction of the Oxford and the Coventry Canals, still popularly known as 'Sutton Stop' after Mr Sutton, the lock-keeper and junction manager for many years in the 19th Century.
One of my favourites is at Autherley Junction, where, in the 1830s, the brand new Birmingham & Liverpool Junction Canal (now the Shropshire Union) linked up to the Staffordshire & Worcestershire canal.
The latter was already nearly 70 years old and profitable, but prone to summer water shortages. The newcomer was several inches lower where it met the older canal at Autherley Junction. Without Autherley Stop Lock,
Here, both are at their summit levels. and if they hadn't built a stop lock the veneral Staffs & Worcs would have had its own water level 'stolen'. Six inches can make quite a difference.
The most curious stop lock is probably at Kings Norton, near the junction of the Stratford Canal and the Worcs and Birmingham. Here, there's a curious 'guillotine gate' arrangement, now permanently stuck in the up position (the different water levels having long since been sorted out).
I was cruising from Birmingham in March, and had just passed through the Kings Norton stop lock when two beefy young men threw rucksacks across the locks, then themselves ran up and JUMPED across the lock - all seven feet of it. I managed to catch the second youth in mid-jump in the winter twilight.
This was my most memorable stop lock experience.
