"Bru" <[email protected]> wrote: >Adrian wrote ... > >> Caen Hill has side pounds. >> >> Bratch has side pounds. >> >> Foxton has side *ponds*. Not the same thing at all. > ><clang> wrong!
I'm afraid not. >Foxton has, technically, side *pounds* not side *ponds* (although they are >usually referred to as ponds) A side *pond* is an unnavigable body of water into which (depending on the type, some or a whole lockful of) water from a lock can be drained and out of which water can be let into a lock. It is provided to allow the lock to be worked using less water than would be required without the side pond.. A side *pound* is a an extension of a (navigable) short pound to the side, provided to increase the surface area of the pound and thus to decrease its variation in water level during locking. Some of these extensions are navigable (e.g. Caen Hill), others are not (e.g. Bratch). As there is no pound between the locks at Foxton (except the passing pound), the bodies of water next to the Foxton locks can't be side pounds. Some side ponds fill from and drain into the same lock. Others (typically at staircases) fill from one lock and drain into the one below. There can be multiple side ponds at a single lock. >In effect, Foxton is not actually a staircase because the locks do not fill >and empty directly from one to the next How the locks in a flight fill and empty has nothing to do with whether it is a staircase. Locks form a staircase if the bottom gates of one are also the top gates of the one below. >At Foxton, there is no bypass and over-filling a side pond (pound) results >in it overflowing haphazardly into the pond (pound) below. Staircases can have no side ponds (e.g. Bingley). In such cases it is easy to flood the towpath, unless there is a way for overflow water in one lock to drain into the one (or the pound) below. IIRC, there are such overflows at some (but not all, unless they've been put in in the last 20 years) L&L locks, maybe including the five rise. Each side pond at Foxton has an overflow allowing surplus water to drain into the pond below. The bottom pond overflows into the pound below 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. ... which extend to the side (and are thus side pounds), and so are (ridiculously) wide. At Famers Bridge, the side pounds are (ridiculously) distorted.. >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. See my definition above. Brian on Harnser <[email protected]> wrote: >On these lock flights apart from the top and bottom locks there are two >paddles. A white one at the bottom of the lock which empties the lock >into the side pond/pound and a red one which fills the lock from the >side pond/pound. >Basically before you empty lock 1 going down, you draw the red paddle >to fill lock 2, the water from lock one is then let out into the side >pond/pound to replace the water used to fill lock 2. The side ponds at Foxton are for saving water. For example, if there were no side ponds there, and you arrived at the bottom of the flight and found all the locks empty, you would have to run ten lockfuls from the summit to pass the locks, and it would take you a long time. However, with the side ponds, you have to run only one lockful from the summit, as you fill each lock from the appropriate side pond. Adrian Adrian Stott 07956-299966
