Ware on Vaults and Bridges. 295 



would be pei'fectly useless to the navigation ; that the water- 

 way at the bridge at even common spring tides rapidly dimi- 

 nishes by the water rising in the curvature of the arches, and 

 of course to a greater degree when the influx is very great. 

 That the current at present is sufficient to carry, in one tide, 

 craft from the Pool to the extent of the up-current, and lighters 

 have occasionally gone from Gravesend to Richmond in a tide; 

 that an increased velocity would not be beneficial to the navi- 

 gation, but on the contrary increase the hazard; that wherries 

 and small craft would not be able to make way against the 

 stream as they can at present ; that any alteration which tends 

 to give the waters of the river a quicker outfall, must injure 

 the navigation ; that the bed of the river near London will be 

 nearly laid dry at the ebb of spring tides, and the filth from the 

 sewers will have a much greater extent of shore to deposit it- 

 self on ; that if the flood-tide ran stronger, the upper parts of 

 the river would be choked with mud cari-ied up from London ; 

 and that less would be carried eastward than at present; for 

 a more than ordinarily rapid current now causes a more than 

 ordinary deposition of filth.' He anticipates that the low lands 

 from Rotherhithe to Battersea, including St. George's Fields, 

 Vauxhall, and Lambeth, will be rendered uninhabitable or un- 

 healthy from damps and stagnant waters. He refers to the 

 fact, easily shown on a map of sewers, that the opposite shore 

 of Westminster, from Privy Gardens to Ranelagh Gardens, 

 was an island, and reasons on the injury the lower parts of the 

 island may sustain. He anticipates injury to the low lands 

 on each shore of the river as high as Kingston. 



" The author has referred to the histories of the Thames and 

 London bridge, in order to reason from the past to the future. 

 It appears that London bridge was built by turning the course 

 of the river ; which confirms what may be deduced from the 

 late probing of one of the piers, ' That the bridge may stand 

 upon piles, but that it does not stand upon stilts' The pro- 

 phecies of its sudden destruction rested upon the stilts, which 

 have now given way under them. Before the bridge was a 

 dam, the river was occasionally so dry, that people could walk 

 over at low water ; and that at high water, they could row 

 their boats in Westminster, Lan)betli, and other low lands ad- 

 joining the river. Since the erection of the waterworks, some 

 of the marshes on each side the river have become towns, and 

 islands have become peninsulas ; by the remoA-al of them, the 

 towns may again become marshes, and the peninsulas may 

 again become islands*. If the increased velocity given to the 

 current, by removing the dam of London bridgCj should cause 



• The nine questions (see CI 5 App. page 1.38. 2d Rep. Lond. Port, \79(]), 

 proposed in 1 740, are not yet answered. the 



