46 REPORT— 1856. 



From opposite Seacombe the Liverpool dock wall extends 4000 yards to 

 the gap in Bootle Bay: by ending it there, only a curved line, similar to that 

 in 1833, shown in the Plan, with a sloping sea-wall, would allow the sea to 

 expend itself in Bootle Bay as heretofore, and act as the eastern side of the 

 funnel of the Mersey, the Rock Channel forming the western. 



The effects these alterations may have had on the levels of the tides in 

 the Mersey, since they were recorded by Mr. Rendel in ISi^, we have no 

 means of comparing, as it will be seen by the before-mentioned table ; they 

 only relate to two tides of that year, which are so much affected by the 

 wind as to form no criterion, it requiring the average of a long period to 

 establish any change in the mean height and flow of the tide. 



We are indebted to Lieut, Lord for the only reliable results derived from 

 the observations of the self-registering tide-gauge at George's Pier, Liver- 

 pool. The discussion of two years of these tidal observations, 1854—55, by 

 Mr. Burdwood, of the Hydrographer's Office, Admiralty, gives the following 

 mean : — 



Datum, Old Dock Sill. Establishment {High Water, full and change) 

 \\^ 35"* Greenwich time. 



High xvater : — ft- in- 



Springs.' — Average height above the sill .... 18 



Neaps 12 2 



Loto water : — 



Springs. — Average height below the sill .... 8 

 Neaps 2 4 



Admiralty, 2nd June 1856. J. BuRDWOOD. 



Lieut. Lord's diagrams furnish the levels of high and low water, direction 

 and force of the wind, and height of the barometer every day in the year, as 

 well as an intermediate line indicating the ordinary sea-level as averaging 

 6 feet above the old dock sill. 



As these observations are to be continued at several stations on the Mersey, 

 we may look upon them as the basis of future observations on the changes 

 in the level and flow of the tides in that river. 



Mr. Rendel's diagrams are very useful, as recording the tidal wave in 1844 

 as well as the relative time of high water at the Bar, New Brighton, Prince's 

 Dock, Runcorn, Fidler's Ferry, and Warrington Bridge. 



From information obligingly furnished to the Committee by Mr. Fereday 

 Smith, Mr. R. Skay, and Mr. Edward Johnes and other sources, we may 

 confidently contemplate the establishment of a record of the tides of the 

 Mersey, both at Ellesmere and other points, with reliable data and informa- 

 tion on the important subject. 



Cheltenham, 12th August 1856. Andrew Henderson. 



Interim Report to the British Association^ on Progress in Researches 

 on the Measurement of Water by Weir Boards. By James 

 Thomson, C.E. 



Belfast, August 6, 1856. 

 Having at last year's meeting of the Association read in the Mechanical 

 Section a short paper on the Measurement of Water by Weir Boards, and 

 having been requested by the General Committee to prepare a Report on 

 the same subject, I beg now to state that 1 have in the meantime been col- 



