188 Mr. Bevan's Abstract of the Results o/Capt. Lloyd's 



levels that the surface of the water at London Bridge, at 

 spring tide high water, is nearly two feet above the sui-face at 

 Sheerness. It may be worth inquiring why the river Thames 

 differs in this respect from other rivers. It would not be very 

 difficult to ascertain the nature of the curve formed by the 

 surface of the water, both at spring and neap tides, by a simul- 

 taneous registering of the height of the water every half-hour 

 for one day, at the respective stages of the moon and tides. 

 There appear to be about eight or nine points where the 

 course of levelling came in contact with the river, where 

 Capt. Lloyd, doubtless, left plain and conspicuous marks to 

 enable any person hereafter to refer to. One person at each 

 of these points for two days, would enable us to see the vari- 

 ation of the surface of the water at the cardinal stages of the 

 tide; and if such a development should be considered of suffi- 

 cient interest, other periods of the tide might at an easy rate 

 be added. At present, it is to be regretted that we know scarcely 

 anything of the physicalconstitution of the most important river 

 in the United Kingdom ; while almost half the inferior rivers 

 have had their longitudinal and transverse sections procured, 

 showing the depth and capacity of the channel, and the power 

 of discharge at different states of the tides. 



The time will arrive when this knowledge will be impor- 

 tant, and when an authentic record of the state of the river 

 in times past will be of the greatest vakie. 



The following is an abstract of the result of Capt. Lloyd's 

 levelling, in reference to a natural zero of low water spring- 

 tide. 



8-5300 Mean level of die sea. 



17"6150 Mean spring-tide high- water mark at Sheerness. 



15'7600 Mean high- water mark. 



13-9160 Neap tide high water. 



15-3159 Marshes of Queenborough. 



50-4265 St. James's standard. 



19-0494! Boundary post of Hoo marshes. 



15-7695 Marshes of St. Mary. 



15-0455 Marshes of Higham. 



24-1015 Three-mile stone on bank of Gravesend canal. 



23-6849 Two-mile ditto. 



22-8259 One-mile ditto. 



22-2375 Iron clamp at second gate on Gravesend canal. 



21-4983 Brass standard on pier at Gravesend. 



18'7168 High water at Gravesend. 



14-1922 Marshfs at Northfleet. 



16-9233 Boundary stone of Swanscomb. 



12-8135 Marshes east of Dartford Creek. 



11-9604 Marshes west of Ditto. 



