(e) Within from 25 to 45 days of the closing of the dam the upland water will have pushed over the dam all the oscillating foul water of the tidal river, and thenceforward the water of the lake will be the same as that of the upper river, and any soilage in it must enter it by sewage or land drainage.
(f) There will thus be obtained by one work a navigable depth of water varying from 65 ft. at Gravesend to 32 ft. at London Bridge, without dredging or any interference with the river bottom or banks.
THE RIVER THAMES BELOW BLACKWALL,
As it will appear when dockised.
But the consequent effects upon the business and usage of the river will be tremendous:—
(g) Ships drawing 30 ft. can then proceed to London Bridge at any hour of the day or night, without waiting for tides.
(h) Ships of all tonnages and draughts can traverse the river, anchor anywhere, lay alongside any wharf or quay, always remain at one level for loading or unloading (an immense boon to shipowners and wharf wharfingers) and need not lie out in the river or obstruct the free navigation.
(i) Dock entrances can be left open, thus saving the cost and time lost in working them. (The London and India Docks Co. estimates the cost of working their entrances at £50,000 per annum.)
(j) There will be no mud entering the docks and backwaters, the water in which will freely circulate with the clean river water.
(k) Exceptional tides, being stopped at the dam, will not overflow the river banks as now sometimes happens.