The River Thames. 67
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THE RIVER THAMES. 67 March 27, 1877. GEORGE ROBERT STEPHENSON, President, in the Chair. No. 1,495.--“ The River Thames.” By JOHNBALDRY REDMAN, M. Inst. C.E.I IT is not even known who constructed the embankments which now regulate the stream in thelower reaches. No one can do more than speculate as to what was the condition of the sand-banks of the estuary before these embankments were raised. The tides must have had free range orer the large areas of the Essex and Kent marshes, now, ordinarily, near the river, 7 feet below the level of highwater of aspring tide; and Wren, ia hisParentalia,” philosophised as to the early conditionof London. Theabstraction of tidalwater on eitherbank for 30 miles inlength and for an averagewidth of only fr mile on either side, by 3 feet in mean depth, would represent nearly 70,000,000 tons. The areas of the Essex and Kentish marshes on the river banks a.n?ount to about 30 square miles; and assuming 3 feet as the average tidal depth, the abo5-e is the quantity of water shut out ; if the average depth were 7 feet the amount excluded would be more than double. Thetotal quantity of tidalwater betweenTeddington and Sheerness may be thus stated :- iym- width. Mean- range. Miles. Feet. Feet. Tons. London Bridge to Sheerness . 43 X 1,500 X 15 = 142,533,482 LondonBridge to Teddlngton. 20 X 500 X 10 = 14,732,143 Grave=d to Sheerness, extra 16 4,000 15 = 141,428,571 width . .l As the last quantity but sliglitly affects the consideration, and as the outline of the river was little altered by these early works, the quantity of tidal water acting upon the river above Gravesend may be assumed to have been reduced proportionately by these 1 The discussion upon this Paper occupied portions of three evenings, but an abstract of the whole is given consecutively. F2 Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 68 MINUTES OF PROCEEDINGS. early embankments. Now, on the supposition that high-water level was raised 12 inches, they would return as an equivalent- Tons. 50 X 1,200 X 1 = 8,839,285 In effect about one-eighth of the volume abstracted. They must, however, have returned a much larger proportion as an equivalent by the deepening of the low-water channel. If the comparison be limited to Gravesend, whichis perhapsmore correct, it would stand thus :- Man- width. Mea11- range. Miles. Feet. Feet. Tons. LondonBridge to Gravesend , 28 X 1 ,500 X 15 = 92,812,500 London Bridge to Teddington,as before . = 14,732,143 Totaltidal column . = 107,544,643 Thus the quantity of water shut out by the embankments may be equal to from five-eighths to three-fourths of the present tidal column, while one-eighth of the quantity abstracted is returned by raising high water. As regards the low-water equivalent, it is impossible to hazard a conjecture of the quantity. Looking at the great depths in the several reaches, the existing course of the river was undoubtedly the low-water channel before the commencement of the embank- ments,whether by the Romans or the Saxons, andthe great conservative agent was then, asnow, the tidal wave. UPPERREACHES. The treatment of the upper reaches of the Thamesis involved in as much obscurity as the lower reaches and estuary. So far back as history extends, the Church appears to have had the monopoly of the fisheries; monks were the residents of the fair slopes of Windsor, and it was from the Church that theCrown obtained the site, since the favourite suburban residence of our monarchs. The establishment of the first locks, weirs, andtheir natural adjunct the mill is in most cases unrecorded; but their names indicate their origin, and the Churchman and Crusader went hand in hand in establishing and profiting by these useful and necessary adjuncts to agriculture. The Temple Mills above Bisham and Marlow, and the Temple Mills on the river Lee, situate at theverge of the tide, had a common origin; they were both founded at the same period by thesame semi-clerical and military fraternity; both were origin- Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. THE RIVER THAMES. 69 ally corn mills, subsequently copper mills ; one afterwards became a paper mill, and the other has now lapsed into desuetude and un- productiveness, and is only commemorative of a regime long passed away. The Abbey Corn Mills at Chertsey, again, show their origin in their name, and the same remark applies to those on the Channel- sea, Abbey, and Mill streams, north-east of London, tributaries of the river Lee, itself a tributary of the Thames. OLDLONDON BRIDGE. Whilst the Church in earlytimes was the great architect of the age, as well as mill-owner, so also it was the civil engineer of the period. The first bridge across the Thames had for its author Peter of Colechurch, a monk, to supply accommodation to the numerous pilgrims passing from Southwark to London. Its history is well known, and for centuries it was the only means of communication from the south to the north side of what is now the metropolitan area, but was then the siteof several towns, London, Westminster, Southwark, Lambeth, &C.,all situate in open country, the twolast under the name of Alsatia, the refuge of the outlaw, and preserving even to the present day its peculiar identity. The fact of London Bridge having been for six hundred years the only means of com- munication north and south has had a wonderful influence in the resultant conformation of the metropolis and the arterialmeans of intercourse ; all themain roads north and south converging towards the bridge. POWERSOF KIVER. As a natural means of intercourse, and as a sanitary agent, the powers and resources of the river have been overtasked to the utmost. It has been treatedin the most fickle and capricious manner, and made an instrument to fulfil the selfish purposes of those resident on its banks. At an earlier period it might, by a general and more comprehensive view, have been made subsidiary to the benefit of the country at large. Various as arethe duties devolving on theriver, being the main drain of the metropolis, supplying potable water, tidal oscil- lation, and, above all, being the carrier of its colossal commerce ; no less numerous are theconflicting interests whichbenefit thereby. The origin of the early locks is obscure; most of them were formed for isolated purposes, andthe constant disputes,even now, be- tween those possessed of abbeyfishing rightsand the general community are only indicative of this spirit. Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 70 MINUTES OF PROCEEDINGS. CONMONS’REPORT, 1799. Thereport of the House of Commons of 1799 on therivers Isis and Thames is perhaps the first public document giving a general view of the then condition of the river. At that time, notwithstanding locks and weirs, those rivers and their tributaries had arrived at such a condition as to demand legislative measures for their conservation. Numerous schemes were proposed for getting over the difficulty, not by the erection of new dams or weirsand locks, but by abandoning the neglected stream alto- gether, and making the river the feeder of an artificial river or canal, to shorten the journey andrender more easy the navigation. Such was Brindley’s scheme for a canal from Monkey Island to Boulter’s Lock, happily never carried out. OLDLONDON BRIDGE.-REMOVAL AND RESULTS. The great result of the inquiry of 1799 was, subsequent to the formation of the large centralarch, the entireremoval and rebuild- ing of London Bridge; the attendant results of which were thc failure of the foundations of Mylne’s bridge at Blackfriars in1836 ; the subsequent partial reconstruction andunderpinning of thc latter bridge, and the quickly following failure of Labelye’s old Westminster Bridge (always faulty), and similar treatment. Both were attacked by the same inveterate symptoms after their appa- rent renovation. At Blackfriars, ten years after the repairs, the river bed was 6 feet lower; and a similar cause produced a like result at Westminster. At the latter site, Page’s elegant structure is supported upon piles and caissons carried down int,o the blue clay so great a depth as to promise it a fair lease ; whilst at Blackfriars the late Mr. Joseph Cubitt, Vice-President Inst. C.E., sank wrought-iron caissons to so great a distance into the same formation as to insurea similar long life ; but there is no blinking the fact, that hitherto on the Thames, as on the Tiber and Clyde, bridgeengineering has been antagonistic to river conservancy, and even now the two are in direct antagonism,notoriously exem- plified by the condition of the foundations of Waterloo Bridge on the Lambet,h shore, with their series of broken Kentish rag stone outwork slopes upon a mud foreshore. It waa designed by Rennie before the removal of old London Bridge, and to the then contour of the bed and low-water regime of the river, the present enormously altered condit,ion of which, especially in theupper reaches, is theresultant of numerous Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. THE RIVER THAMES. 71 causes. That the removal of old London Bridge was not the sole one is evidenced by the continued and progressive lowering of the river bed and of the low-water level ; it was the main cause, but it was followed subsequently by numerous other active agents- the removal of old Westminster and Blackfriars bridges being the chief-the attendant results to navigation area progressive lower- ing of the river bed.