The River Thames. 67
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.
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