from the Removal of London Bridge. 25 



past two o'clock, there is a rise of 1 7i feet only. The action 

 of the tide is now affected by the bridges, the regular progress 

 of this wave being checked, and the surface of the high water 

 declines all the way to Putney, where it is high water at a 

 quarter past three o'clock ; but from thence again there is a 

 rise of one foot to Teddington, where it is higli water at three- 

 (juarters past four. Hence observe that from Billingsgate to 

 Teddington the wave passes at the rate of 8 miles per hour 

 only ; while below Billingsgate the same wave of high water 

 passes at the rate of 20 miles per hour, or more particularly 



Time. 

 Miles. Hour. Minutes. Miles. 

 From the Nore to Gravesend 18 in 1 is 18 per ho. 

 Woolwich 15—1 — 20 

 Deptford 61 — i — 26 

 Billingsgate 4; — i — 16 

 Swan Stairs, a loss of 10 — 

 Putney 7 in 50 — 8^ 



Teddington 11 — H — 7^ 

 It is obvious then that this rapid diminution of the velocity of 

 hicrli water is caused by the narrow at London Bridge, and 

 that, were that obstruction removed, there is every reason to 

 l)elieve the velocity in the upper river would be greatly in- 

 creasetl. 



It must also be observed that the fall or difference of height 

 between the surfaces above and below bridge at high water 

 must not alone be taken as the proper measure of the obstruc- 

 tion, and used as a datum throughout a calculation, because 

 the fall through the whole tide is much greater. ^ In one very 

 moderate spring-tide, which I observed on the 26th of May 

 last, when the fall at high water was only 5 inches, the fall 

 through most of die preceding part of the tide had been 14- 

 inches. 



The high water will therefore go up to the head of the tide- 

 way more speedily, and will rise higher than at present. 



Secondlij, Of I he JRlver at Loiv JVafa: 

 This water must also return with greater velocity, and the 

 removal of the bridge will not only permit the increased head 

 to pass off at the ebb, but likewise that portion which is now 

 retained by the obstruction. 



Were the flood tide not to return, and the stream of the 

 river to cease, the bed would exhibit a series of ponds at levels, 

 gratlually increasing in elevation as we pass to the westward; 

 of whicii the first would extend to Battersea Bridge, liaving a 

 shoal at Westminster Bridge, on which there will be little or 

 \'ol. 6'J. No. 303. J/dij 182.'3. D no 



