Autobiography of Sir John Rennie, F.R.S. 31

Autobiography of Sir John Rennie, F.R.S. 31

At that time a former Act rendered it necessary that before any

improvement was made in any port or harbour, a Commission should be

appointed by the Admiralty to investigate the plan, the Commission to

hold its inquiry in public; Captain Washington and Captain Veitch were

appointed by the Admiralty for this purpose. They held their court at

the townhall, Lynn, and, singular to relate, the gallant gentlemen

advocated a curved instead of a straight channel, which, under the

circumstances, was so contrary to the practice of every good hydraulic

engineer, that their report was simply ridiculous, and when produced

by the Admiralty before the Committee of the House of Commons on the

Bill, was proved by the best engineers to be wrong, and was therefore

ignored by the Committee, and the plan proposed by Mr. Stephenson and

myself was unanimously adopted. The Bill accordingly passed, and the

agreement between the Middle Level Commissioners, the Corporation of

Lynn, and the Company, the two former contributing 60,000_l._ each, was

ratified; still there were several restrictive clauses, such as entailing

the maintenance of the works upon the Company, giving up the whole of

the green marsh to the several frontages, which materially abridged

the profits of the Company, and increased their risks, and which I in

vain protested against. The main cut commenced on the lower side of

Lynn, and was continued in a straight line 2½ miles. We calculated that

certain dimensions were ample in the first instance, because it was not

necessary to excavate the cut artificially to the full depth, as we knew

that as soon as the current began to act upon it, it would in a short

time be adjusted to its proper capacity for the admission and discharge

of the tidal waters, in the same manner as had taken place in the Nene

estuary outfall already mentioned. From the lower end of the above cut

the channel for a distance of two miles farther to deep water was to be

trained through the sands, formed by guide walls of rough stone raised to

about the level of half tide, with beacons upon it at certain distances

to indicate the channel; and when once the channel had been thus trained,

the remainder of the banks to their full height above high water would

be raised naturally by the silting up on each side, combined with the

gradual process of embanking the land from each of the shores of the

estuary, if properly managed.

 

Messrs. Peto undertook the contract of the main cut. The land having

been bought, and everything arranged, a day was fixed for turning the

first sod, at the upper end near Lynn. The ceremony was performed by the

late worthy Sir William Foulkes, the chairman of the Company, on the 1st

of November, 1850. On that day a grand procession, consisting of the

Company, the Corporation and trades of Lynn, the Earl of Leicester, Lord

Lieutenant, together with numerous gentry, and other spectators, attended

the ceremony, which went off with great _éclat_, and the whole, as usual,

terminated with a grand dinner to about two hundred persons at the

townhall. Unfortunately my friend Mr. Stephenson was abroad and could not

attend. The excavation of the great cut proceeded rapidly for some time,

until Mr. Stephenson and myself, judging that enough had been done, and

that the current would do the rest more effectually, ordered the dams

to be removed at both ends and the water admitted, which was accordingly

done. As soon as the fen proprietors heard of this, they were greatly

alarmed; they said that the Company had violated their agreement with

them, and had gone contrary to the Act of Parliament, in not excavating

the cut to the full depth required before letting the water in. We

endeavoured in vain to persuade them to the contrary. They immediately

applied for a mandamus to stop the works and restore the dams until the

cut had been excavated to the full dimensions required by the Act, and

obtained an injunction, so that we were compelled to restore the dams and

stop out the water. We determined, however, not to give up the point,

and argued the question before Vice-Chancellor Turner, and were beaten.

We then applied to the Admiralty, who would not assist. We appealed from

the Vice-Chancellor’s decision to the Lords Justices of Appeal, and were

again beaten; still we would not give up, and at last we found that there

was no alternative but to get a new Act of Parliament allowing us to

make the cut in any manner we pleased, provided that we made it of the

dimensions originally agreed upon. The Eau Brink Commissioners opposed us

by every means in their power, but our evidence, which was given by the

first engineers of the day, so completely satisfied Parliament that we

carried our new Bill as we wished it.

 

Thus, after a severe struggle for two years, we carried our point; but

this was so much valuable time lost, besides a great deal of money spent

in litigation. Having obtained our new Act, we set to work immediately

to remove the dams of the cut, and to let the water in, and at the same

time to commence the dam for stopping up the old channel of the Ouse at

the lower end of the town of Lynn, near the upper end of the new cut.

As the dams and bottom of the river near them were composed of strong

clay, it took some time to remove them so as to admit the waters freely

into the cut; but as soon as this was done, the scour began to have a

sensible effect; this was increased by the closing of the dam across the

old channel, so that within a few months afterwards not only had the

new cut been scoured out to the full depth required by the old Act, but

considerably beyond it. Thus Stephenson and myself were proved in the

right, and the opposition entirely in the wrong.

 

The effect on the port of Lynn was very remarkable. The depth of water

at spring tides was 18 to 20 feet, and neaps 14 to 16 feet; and there

was a regular depth at low water of spring tides of 9 to 12 feet in

the cut, so that the largest vessels could always come up and depart

with their full cargoes either at spring or neap tides, and the channel

was so direct and easy of navigation, that pilots, of whom there was a

large establishment, became in a great measure unnecessary, and their

numbers were considerably reduced as well as their charges, and the

increase of trade soon enabled the town of Lynn to pay off the 60,000_l._

contribution to the estuary works.

 

The drainage interests also derived a similar benefit by the lowering of

the low-water mark 6 feet, which, together with that obtained by the Eau

Brink Cut, was altogether 11 feet. The Middle Level Drainage, upon which

a large sum had been expended, obtained an increased fall of between 3

and 4 feet, which enabled the Commissioners to drain the greatest portion

of their lands naturally instead of artificially. In fact, the Port of

Lynn by means of these works has become one of the best on the east

coast of England, at the least expense, and with the most moderate dues;

indeed, if the Drainage and Navigation had paid double the money which

they did to this great work, and which in justice they ought to have done

for the benefits it has conferred upon them, they would have been more

than amply indemnified.

 

The Estuary Company having now completed the cut, turned their attention

to the best means of reclaiming from the Wash the 35,000 acres which had

been allotted to them by the Crown, or at least as much of it as they

could; but unfortunately there were so many different opinions among them

and their advisers, that they lost a great deal of time and money in

pursuing improper measures. I, who originally designed the undertaking,

and had acquired great experience in this department from having carried

on successfully similar works in the Great Wash and elsewhere, always

adhered to one system, namely, to work with nature, and never to go

against her; if we did, I invariably found that we were beaten.

 

We knew, from a variety of experiments that had been made, that the

alluvial matter held in suspension by the waters in the Great Wash was an

ascertainable quantity; that this alluvial matter was transferred from

one place to another, according to the prevailing winds and currents;

and that it was only deposited where circumstances were favourable, such

as eddies and sheltered stagnant places. Now my great object (after

having confined the fresh and tidal waters of the river Ouse to one

adequate channel, so as to preserve the drainage and navigation in an

efficient state) was to cause to be deposited the alluvial matter that

was held in suspension in the waters spreading over the other parts

of the estuary. This could only be done effectually by arresting the

progress of the flowing and ebbing waters in such a manner, that as much

of the alluvial matter as possible might be deposited in the places most

convenient, that is, in those places where it was desired to raise the

soil above the level of high water of neap tides. When this level is

reached grass may be expected to grow, and in a very short time the

whole is converted into a green marsh. The process simply this: when the

deposit has reached a certain number of feet above low water of spring

tides, a species of light green vegetation first covers the surface in

patches, then by degrees extends over the whole; the reclaimed land

still continues rising, and at a higher level above low water samphire

makes its appearance; the accumulation of soil still goes on increasing,

when the samphire disappears, and grass succeeds it, and in a short time

afterwards the place assumes the appearance of a level green marsh well

adapted for grazing cattle. After it has arrived at this stage, which it

does at about the level of high water of neap tides, the accumulation

is very slow; on our coasts it seldom attains a much higher elevation,

except where the sand is blown up by strong winds from the sea, which

forms dunes or banks, that, as in the case of Holland and other places,

sometimes attain an elevation of 30 feet and upwards above the level of

the highest tides. This, however, is not the case around the shores of

the Great Wash; there the marshes are simply produced by the gradual

deposit of alluvial matter in the manner above stated.

 

The great object, therefore, as I have said, is to facilitate this

deposit or accretion as much as possible by artificial means. Nature,

if left to herself, though sure, is very slow. We must therefore assist

nature, by following and working in unison with her laws. We must go

to work gradually, and not by great and expensive operations check the

currents violently and at once, which would only produce an equally

strong current elsewhere, so that while we gained in one place we should

lose in another. By a series of light works composed of bushy fagots or

other similar materials, raised about 12 or 15 inches above the level

of the sands, and disposed in a series of lines at certain distances

from each other, not continuous, but in lengths, so that the ends may

overlap each other, the currents will be gently checked without being

wholly obstructed, the water between them will be rendered stagnant, and

the alluvial matter with which it is charged will be deposited. When

the deposit has reached to the top of these works, the works themselves

should be raised higher in the same place, or in an intermediate

position, as circumstances shall render advisable. Where a certain space

is intended to be raised or warped up, it is generally better to commence

at the upper end and work downwards; the works themselves are less

expensive, the height to be raised is less, and the water impelled by the

mass of the tide behind brings up a greater quantity of alluvial matter,

and in proportion as the space above is warped up it accumulates in a

greater degree below. In carrying on works of this kind, wherever we find

that there is a tendency to make a channel, and with it a strong current,

it must be checked gradually from the upper end, so that the quantity of

water passing through it may be decreased, and this channel will soon

fill up. When a certain space has been naturally or artificially raised