In this way the discharge of effluents at Crossness and Barking passes up and down in front of London for more than a month, and it becomes apparent that the tidal action keeps the river continually saturated with about 45 days’ soilage. It is no wonder, therefore, that the conditions of colour, smell and turbidity of the river below Teddington are so vile as compared with the Upper Thames, especially as to the above sources of filth must be added the tidal current, which is so rapid that it keeps the mud continually in suspension, washing it up at one time, depositing it at another, but never permanently leaving it except in the places unscoured by the upland water, such as docks, backwaters and places out of the main current. It has been acknowledged by all writers that if the upland water should be stopped the Thames would become a stagnant oscillating ditch, because all filth discharged into it would remain in it permanently.
The docks trap a very large proportion of this mud, and it costs at least £60,000 per annum to clean it out. The mud enters with the locking water and with that pumped to make up the basins.
Effect of Dockisation on the River.
It is proposed to construct across the river at Gravesend a dam or barrage similar to that across the Nile, containing numerous adjustable sluices, and in addition a series of very large locks, the dam to hold up the river to about Trinity high-water level (see section, [Fig. 4]).
The immediate effects will be these:—
(a) The tides, Neaps and Springs, will be stopped at the dam.
(b) The river will be converted into a long lake having numerous affluents, the principal of which will be its natural flow over Teddington Weir.
(c) It will have a slow downward current, never reversed, so that all that enters it will pass downwards to the dam.
(d) Its level (normally at Trinity high water) can be regulated to any level above low water by the sluices.