22 Mr. Telford oti ihc Effects on the Thames 



perintended and occasionally inspected the proceedings: I 

 have also received the tidal observations made at difterent 

 times at several stations upon the river. 



In order to proceed with regularity, I shall adopt the fol- 

 lowing arrangement in tracing the effects which would be pro- 

 duced to the westward and also to the eastward of London 

 Bridge, if the present edifice, which constitutes a dam of from 

 1 foot 1 inch to 5 feet 7 inches, or 4 feet 4 inches on an aver- 

 age, were removed, and in its stead a new bridge, with com- 

 paratively little obstruction, v.ere substituted : 



1st. Observations on the comparative state of high water, 

 founded on the surve3's and levels lately taken, and the tidal 

 observations made in 1820, 1822, and 1823; and further, 

 what is likely to take place if London Bridge be removed. 



2dly. Similar observations as regards the state of low 

 water. 



3dly. As to the effects which the aforesaid changes are likely 

 to produce upon the navigation, bridges, banks, wharfs, shores, 

 and adjacent properties. 



First, As to the State of the River at High Water. 



It appears from the table of observations of the height of 

 the tides at the several bridges in 1820 and 1822, that the 

 average fall through London Bridge at high water was from 

 8 to 13 inches; that by those of 1823, since the removal of 

 the water-works, the fall instead of 8 inches is now only from 

 3 to l inches ; I think therefore it is fair to conclude that with 

 a still less obstructed waterway there will be little or no fall 

 at high water, and that hereafter high tides in the western 

 parts of the city will even in calm weather be at least on the 

 same level as below bridge. I find that the level of the wharfs 

 below bridge is from 2^ to 4 feet above the Trinity datum, 

 and that those of 2^ feet are occasionally flooded. The aver- 

 age level of the wharfs above bridge is from 1 V to 2 feet 

 above the Trinity datum; and the extraordinary flood of 

 1821, which rose at Teddington 7 feet, rose at Putney only 

 2 feet, and at Lambeth 1 foot 1 1 inches above the said datum. 

 Therefore it appears that there is more reason at present to 

 dread the elevation arising from the tide below bridge, than 

 from^ floods above ; and diat the floods of the Thames are not 

 sufiicient, in the p esent state of diings, to fill the lagoon or 

 pond above the narrows of the bridge to the height which 

 some of the tides do below, and which, there is reason to be- 

 lieve they also would above, were the channel unobstructed. 



But it may be supposed that the quantity of tide coming in 

 at the Nore being given, the additional space provided for it 



by 



