26 Mr. Teltbrd 07i the Effects on the Thames 



no water, and nearly 2000 yards in length. The second pond, 

 from Battersea to Putney, would be 16 inches higher than 

 the former. At Putney Bridge would be a rise of 1 7 inches. 

 Above Putney to Mortlake is a shallow channel with small 

 pools ; in the deepest passage across the bars there is now less 

 than 3 feet of water. Mortlake is the next pond, two miles in 

 length. Its surface is level with the present low w ater at Lon- 

 don Bridge ; but before the construction of that work it would, 

 as its name implies, have been a dead or stagnant lake at low 

 water. The other ponds which are higher than the present 

 low water may be observed in the general section. The depth 

 over the bar is no where less than 2^ feet, or more than 4 feet ; 

 but this depth is with some difficulty sufficient at present for 

 navigation to the locks at Teddington. 



Were the river water to be run oflP above bridge, this navi- 

 gation must cease, imless a new channel be excavated through 

 the shoals : independent of the depression in the lower pond 

 which the New Bridge will permit, a longer time will be given 

 for the ebb to empty the upper reaches, as we may see by in- 

 quiring whether the obstruction of London Bridge occasions 

 any remarkable deviation from the progress of the ebb, as we 

 have just found it to do in the case of the flood tide, whereby 

 we form some judgement of the probable result of its removal 

 with respect to the velocity of the ebb stream. 



Allowing therefore that the tide at the Nore occupies 6 hours 

 1 6 minutes, or the regular half tide, we find that low water 

 proceeds — Time. 



Miles. Hour. Minutes. Miles. 

 From the Nore to Gravesend 18 in 1 24 ) ,„ , 



Woolwich 15-1 8/ 13 per ho. 

 Deptford e\ — 37^ lOf 



Billingsgate 4 — 22^ 10 

 Old Swan, a loss of 20 



Westminster 2 in 22^ 5 

 Putney 5\ — 1 34 3^ 



Teddington 11 " — 3 20 3| 



which exhibits the same rapid changes of velocity caused by 

 the bridge as in the case of flood. 



Were the bridge removed, therefore, it is evident that the 

 velocity of ebb above bridge would materially increase, the time 

 of low water be earlier than at present, the drainage of the 

 upper ponds more complete, and the navigation which is now 

 practicable up to Teddington would cease too early near that 

 place. 



Thirdly, Effects to be produced. 



And lastly, from the foregoing statement of facts it has been 



shown 



