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I've been reading about the recent flooding in Somerset, and came across this:-

Floodwater is removed from many of the moors of the Somerset Levels by pumping stations, which were originally steam-powered. These were superseded by diesel engines, and more recently by electric pumps. The King’s Sedgemoor Drain is unusual in that it operates entirely by gravity. Consideration was given to replacing Dunball clyse with a pumping station in 2002...

This word doesn't appear in any online dictionary I can find; the nearest is clysis, meaning:-

the administration of an enema.

which, whatever your views on Somerset, is probably not what is meant. There's a video of Monk's Lease Clyse in action here. Which bit is the clyse?

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See also english.stackexchange.com/q/18479/8019 . – TimLymington Feb 16 '14 at 12:11
You might be interested in the Wikipedia page for King's Sedgemoor Drain, artificial drainage channel which diverts the River Cary in Somerset into the River Parrett at Dunball near Bridgwater. The proper noun names of three of the drainage inlets are Dunball Clyse, Cowhouse Clyse, Monks Leaze Clyse. The author uses the non-capitalised version several times to refer to those sluices and proposed extensions thereto. There's also Greylake Sluice, Nythe Sluice, etc. (he uses sluice for those, and all the other "generic" references). – FumbleFingers Feb 16 '14 at 13:11
up vote 6 down vote accepted

According to the OED definition, it is a local/regional word that means the same as clow. There is only one attestation quoted, from Somerset:

1882 Spectator 6 May 595. In the Reports of the Somerset Drainage Commissioners, the sluices and locks under their jurisdiction are called ‘Clyses’.

Obviously, clow is not exactly a common word, either, but it does seem to be more common than clyse, with about thirty or forty attestations in two meanings (actually three, but one is noted as being obsolete and has a question mark, but no attestations—so slightly paraphrasing the entry numbers here):

  1. A sluice or floodgate: ‘esp. (a) The outfall sluice of a river or drain communicating with a tidal river and provided with flood-gates’. (b) ‘A shuttle in the gates or masonry of a lock, which is raised to admit or discharge water; a similar arrangement by which the admission of water to the wheels of water-mills is regulated’. Peacock Gloss. Manley and Corringham (N. W. Lincoln).

  2. A sluice or sliding door for other purposes.

So a clyse would appear to be just a regional Somerset word for a sluice, basically.

It seems that clow is a false singular, based on an earlier form clowes/clowis. This was originally a singular itself (from Old English clūse, meaning ‘enclosure’, and related to ‘close’, both from the nominalised Latin passive participle clausa ‘closed’, from the verb claudō ‘to close’), but was reinterpreted as clow + plural -es around the 15th or 16th century.

Clyse is less certain: it appears to be from French écluse (same word as the Old English cluse), or perhaps it just represents a dialectical nonce rounding of the u in the Old English, yielding regional *clȳse as a variant of clūse.

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Refer to "Wetland, Life in the Somerset Levels" by Patrick Sutherland and Adam Nicolson (1986). "The only means of preventing the sea-water rushing miles inland up the rivers are the great doors called clyses which were fixed across the mouth of the Brue at Highbridge as early as 1485... The clyse doors are the great Canute gestures of the Levels, the grandest of all efforts to shut the Levels off from the sea... It is the simplest of technologies: the pressure of the flood tide forces the clyse shut into the mitre of lock gates; and the ebb releases them. They are the clearest Levels image of separation, of sorting land from water." One problem for the people of Somerset is that the Parrot estuary is too wide for clyse technology, so when the tide surges, it washes sea and fresh water back onto the land.

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I don't know the origin of the word clyse. However, what a clyse does is a bit different to most sluices. The water coming off the Somerset Levels (such as down the King's Sedgemoor drain) is fresh water, not sea water. Nor is it tidal. Also the level of drains on the Somerset Levels is usually a bit below the high tide mark of the river. The estuary of the River Parrett at that point is tidal and mostly sea water. You don't want sea water going back up the drains into the Levels and affecting the land by adding salt. So a clyse is a sort of one-way valve that is regularly operated to allow excess fresh water out into the tidal river when the level in the river is below that of the drain, but does not allow sea water back up the drain into the Somerset Levels when the level in the river is above that of the drain.

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I read somewhere that some dutchman worked on the SL some centuries ago. Being dutch there are, depending on the pronunciation of clyse, the words "kluis" en "sluis" that are old enough and both have meaning in civil engineering. Wikipedia gives an expanded solution to OED and further reference. Sluis (dutch) => Sluice (english => Clyse, http://en.wikipedia.org/wiki/Sluice. Clow does not ring a dutch bell.

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So basically you're saying that "clyse" might be a Dutch-influenced spelling of "sluice"? How did you arrive at this conclusion (or am I misunderstanding you completely)? Also, (1) what does the "SL" in your first sentence mean, and (2) where does "Clow" enter the question at all? – Marthaª Feb 26 '14 at 21:36
@Martha, I think this answer is a kind of combined comment to the previous answers: SL is probably the Somerset Levels, and clow is mentioned in my answer. – Janus Bahs Jacquet Feb 27 '14 at 0:52

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