[EMAIL PROTECTED] wrote: > It makes you realise what an astonishing bit of engineering was the HNC, > being the highest, shortest and most direct route across the Pennines, it > nevertheless DOESN'T have a deep lock in the list.
NIcholson's doesn't quote any depths for the HNC locks, but my memory is that while they are mostly a couple of feet deeper than the typical 7-8ft of the average narrow lock, there aren't any really deep ones. Is that right? I wonder... out of all the deep ones we've come up with so far, what proportion are (a) on an early canal dating from before engineers figured out the importance of keeping water use down by evening-up the lock heights or (b) the result of modifications not planned when the canal was designed (eg the trial lift at Tardebigge and the various replacements of two shallow locks with one deep one) or (c) on a waterway where water supply wasn't an issue (eg the Manchester Ship Canal which is river-fed). I suspect most of them. Martin
