Adrian wrote ... > Caen Hill has side pounds. > > Bratch has side pounds. > > Foxton has side *ponds*. Not the same thing at all.
<clang> wrong! Foxton has, technically, side *pounds* not side *ponds* (although they are usually referred to as ponds) In effect, Foxton is not actually a staircase because the locks do not fill and empty directly from one to the next, they fill and empty through a pound off to the side of the lock. It is, to all intents and purposes, a flight of conventional locks compressed into a very small space. In a conventional lock flight, opening the bottom paddles of one lock before starting to fill the next lock down is usually not a catastrophic problem because either a> the intervening pound can contain the water or b> the water runs over the bypass weir (to waste) or over the gate weir (better). At Foxton, there is no bypass and over-filling a side pond (pound) results in it overflowing haphazardly into the pond (pound) below. The excess water cascades down the hillside, damaging the earth banks of the side ponds (pounds!) as it goes until it overflows across the road and down the slipway at the bottom of the hill ... usually flooding the pub in the process. Cane Hill - also side pounds although differing from Foxton in that the paddles are in the gates, not the side wall of the lock and the side pounds extend from between the locks. Bratch, IIRC (and I stand to be corrected here) has neither side ponds nor side pounds. It has ridiculously short pounds between the locks. So at both Foxton and Caen Hill ... and most other flights of locks for that matter, you empty and fill the locks into and from pounds of water. It doesn't matter whether the pounds are long stretches of water in between the locks or off to the side at 90 degrees to the line of the canal. Nor does it matter where the paddles are located (ie; on the gates, in the lock wall etc.). Nor does it matter whether the locks have a stretch of water in between them or not. The underlying principal of operation is just the same. Although the opportunities for spectacular cock-ups may vary! On a true staircase of locks, such as Grindley Brook, there are neither pounds nor ponds between the lock chambers. Each chamber is emptied directly into the one below it and filled directly from the one above. Now a side *pond* is a different beasty altogether. Side ponds are (were) a water saving device. A side pond is a chamber built alongside a lock chamber into which the lock can be *partially* emptied. When the lock needs filling, it can be *partially* filled from the side pond. Use of a side pond is not essential and they were only brought into operation when water was short. To use a side pond requires a degree of intelligence and familiarity with the particular setup (with neither of which BW credits modern boaters hence the disappearance of side ponds!). Emptying a lock ... *if* the side pond is empty, the side pond paddle is raised. When the side pond and the lock chamber achieve a level, the side pond paddle is dropped and the bottom gate paddles are raised to finish off emptying the lock into the pound below. Filling a lock ... *if* the side pond is full, the side pond paddle is raised. When the side pond and the lock chamber achieve a level, the side pond paddle is dropped and the top gate paddles are raised to finish off filling the lock from the pound above. Note the key difference from Foxton - the side pond is used to (partially) empty and fill the *same* lock. The ponds (pounds) at Foxton etc. are used to (completely) empty one lock and fill the one below. That's the critical difference between a side pond and a side pound. Using the side pond will save, roughly, half a lock full of water at best. Misusing it can waste a great deal more! Regards Bru
