CllAP. VIII.
539
In the year 1631, Sir Nicholas Vermuyden was consul toil upon the subject, ami his firstwork in England was to complete the embankment of the Dagenham marshes ; after whichhe drained Hatfield Chase.
Ninety-five thousand acres were to be given as a reward for draining the great level,which was undertaken by a company of adventurers, with the Earl of Bedford at their head,lie at that time possessing 20,000 acres in Thorney and Wittlesev.
The works were entrusted to Vermuyden, and carried into effect in the following order: —The old Bedford river, 21 miles in length, and TO feet in width, was improved from Erith to Salter's Lode; same cut from Eeltwell in Norfolk to the river Ouse ; Sandy’s Cut, nearEly, 2 miles in length, and 40 feet in width ; Beviil's Leam, 10 miles long, and 40 feet inwidth, from Wittlesey Mere to Guyhorn ; Morton’s Leam; Peakirk Drain. 10 miles longand 17 feet wide; New South Eau, from Crowland to Clowes’ Crop; Hell’s Cut, nearPeterborough, 2 miles long and 50 feet wide ; Shire Drain, from Clowes’ Crop to Tyd andthe sea ; two sluices on the Shire drain ; a clow or dough at Clowes’ Cross, a kind ofsluice, in which the aperture is closed by a sliding board in the manner of a porte cuulise ;a great sasse, or navigable sluice, through which any thing could pass at pleasure, at the endof the well creek at Salter’s Lode; another stone sluice at the mouth of the Bedfordriver ; a sluice at Erith ; a larger one at the Ilorse Shoe, below Wisbeaeh, to keep the tideout of Morton’s Leam.
In the year 1C35 a charter of corporation was granted to the Earl of Bedford and others,and the work having been declared complete, the 95,000 acres were set out by his Majesty’ssurveyor, which were, however, only summer lands.
The law hv which this allotment was made was reversed, and the Earl of Bedford diedin 1641, tlie victim of disappointment.
Vermuyden divided the fens into the North, Middle, and South levels ; the space betweenthe Welland and None was called the North Level; and the first of these rivers was pro-tected by a hank 70 feet wide at the base, and 80 feet high. The Middle Level eastward ofthe None, was protected by Stand Ground Sluice; and the waters of the Ouse wereconfined for some distance by a bank 60 feet wide at the base, 10 feet at the top, and 8 feetin height. In the South Level a new river channel was made, 120 feet in width, and 10 feetin depth, with sluices at each end.
Vermuyden, who had studied in Holland, seems entirely to have mistaken the nature ofthe English fen district, his whole scheme being directed to keep out the sea, sluicesbeing placed at the ends of all his canals, as well as those of the natural rivers, for thispurpose. Ilis object should have been, by raising the embankments of the great drains,to allow the tidal waters to flow freely up them, and thereby prevent the mouths ofnatural and artificial outlets from being choked up.
The sea never rises above a certain known level, and banks may be always formed to keep itout; in these districts there is more to be dreaded from the freshes after heavy rains, andto collect and allow them a free passage into the ocean is the most important consideration.The passages or drains should be cut as straight as possible, the current being regulated bythe declivity of the bed, and this will be greater as the line is shorter : 3 or 4 inches permile constitutes a moderate current; consequently if the distance is doubled with the samefall, scarcely any current is obtained. All obstacles, as sluices, which prevent the tideentering or the drainage water from freely passing oft', should be avoided. Three inchesfall per mile makes a slow movement, 4 inches a moderate velocity, and sufficient for alldraining operations, so that any sill laid down at the mouth of a river, 3 feet above theproper level, will have the effect, where the fall is 3 inches to a mile, of obstructing thenatural drainage for 12 miles above it. A drainage outlet obstructed by sand banks hasthe same effect, the fall being lessened in consequence of the deposit at the mouth. Freeingress should always be given to tidal water, and the banks of the river raised sufficientlyhigh to obtain a good and perfect fall, and the course should be as straight as circumstanceswill allow, that none of the advantages be lost. An increased downfall, as well as tidalwater, may be also rendered efficacious in removing old sand banks, and is the best methodof scouring a harbour
The Eau Jiranch cut , opened in 1821, and excavated under the direction of Mr. Rennie,was one of the greatest improvements effected in this district: its cost was 33,000 pounds;and the first winter it was opened the river channel from Denver Sluice to Lynn was scoured5 feet, since which time it has gradually deepened itself nearly 15 feet on an average: allthe outfall sluices on each side of the river, and the beds of the drains have been lowered,and the windmills used are no longer required.
This was originally projected by Nathaniel Kinderlev, about 1720, and was intended toconduct the Ouse by a direct cut from Eau Bank to Lynn, a distance of only 2£ miles,instead of allowing it to flow 5 miles. The tide in Eau Bank flows three hours, and risesin that time 15 feet; thus leaving nine hours’ ebb.
The \<i/e Outfall is a new tidal channel, carried through the light sands which borderthe Lincolnshire coast; that portion which is artificially formed commences about 6 miles