40 REPORT — 1856, 



Between 1833 and 1837 was perfected that remarkable change in the 

 northern outlet of the Mersey, of which Capt. Denham has recorded so many 

 important particulars in his ' Sailing Directions,' and in communications to the 

 Association. But there is such a complete dearth of observations upon the 

 changes which preceded the opening of this new outlet in 1833, and upon 

 the meteorological phaenomeua by which they were preceded, or accom- 

 panied, that the result of any detailed inquiry must necessarily be extremely 

 precarious. The same observations apply to periods immediately subse- 

 quent and precedent to Capt. Thomas's survey in 1813. The general 

 features of the consolidation and enlargement of the principal sand-banks, 

 and also of the eastern shore of tiie estuary, may be observed upon this 

 survey, and also upon all the authentic surveys since that of Capt. Collins in 

 1689. It is also remarkable that the low-water margin of the eastern shore 

 appears to have advanced westward to an extent fully equal to one-half the 

 width of the northern channel as laid down by Collins, or 1000 yards. 



From a report of Mr. George Ilennie, C.E., to the Corporation of Liver- 

 pool, in 1838, it appears that at that time upwards of 13,000 acres had been 

 abstracted from the tidal area of the river, the original extent of which is 

 estimated at about 35,000 acres, and these abstractions were principally in 

 the upper part of the river. Since then no important abstractions have been 

 made without the sanction of Parliament. 



The tidal area appropriated to the dock purposes of Liverpool alone since 

 1650 amounts to 784' acres, exclusive of the open basins ; of these, 4'70 acres 

 have been appropriated within the last fifteen years. 



From the foregoing remarks it appears that the changes in Liverpool Bay 

 are to be attributed principally to the influence of freshes, droughts, wind, 

 and the reduction of tidal area ; and that remedial measures adopted for the 

 maintenance or improvement of the approaches should be specially designed 

 to cooperate with these forces. 



It may perhaps be thought that sufficient consideration has not been given 

 to the very large amount of silt, which, according to Capt. Denham, in his 

 paper in the 'Reports' of the Association (1837), is being constantly 

 washed down by the river and deposited in the bay. 



The attention of the Committee has so far been confined principally to the 

 phgenomena of the bay. Captain Denham supposed the silt to be derived 

 from the shores of the upper part of the river, where there is no doubt that 

 the tidal water continues to encroach upon the land. From the geological 

 formation of this land, a large proportion of the silt must consist of clay and 

 mud, with but a very small proportion of sand. The former, from its levity, 

 is mostly conveyed away by the ebb tide, a thin deposit being only temporarily 

 left upon the sandy shores and banks of the upper and lower estuaries, which 

 is either dried up and dissipated by the wind, or removed by those neap tides 

 which are too low to be able to continue the encroachments of the spring tides. 

 Two local changes seem to require special notice before concluding this 

 Report : — 



1st. The waste of the clay cliff's in Cheshire, from Seacombe Point to 

 North Egremont, which has now been going on to a considerable extent and 

 for some years. This, there can be little doubt, is a consequence of the North 

 Dock-works of Liverpool, by which the river has had its channel much con- 

 tracted, and has naturally sought its equivalent from the opposite and weaker 

 side. 



2nd. The waste on the Cheshire shore, adjacent to Leasowe Castle, west- 

 wardly. According to Mr. RoUett, the acting-surveyor of the Wallasey Em- 

 bankment, under the surveyor to the Corporation of Liverpool, this waste has 

 averaged 6 yards per annum for nearly thirty years past. It is, however, con- 



