THE RIVER MERSEY. 3 



increase in the sizes of the banks, the growth having been both lateral and 

 vertical ; some of the fluctuations are very remarkable ; that the average 

 area of the northern, channel remains very stationary, though in places the 

 mutations have been considerable ; and that there has been a diminution of 

 average area in the Rock Channel, arising from a deposit of silt at the 

 eastern end. This channel is the oldest known entrance into the Mersey ; 

 it is laid down by Captain Collins in his survey of 1689, who says of the 

 northern channel (by way of Crosby and Formby) that it is not buoyed or 

 beaconed, and so not known. There appear to be grounds for serious ap- 

 prehensions that the Rock Channel may be irrecoverably lost, if due pre- 

 cautions are not adopted in good time. 



There have been extraordinary fluctuations in the seaward entrance of the 

 northern channel within the period embraced in this inquiry, and at this 

 present time another great change is being accomplished, namely, the sub- 

 stitution of the Queen's Channel for the Victoria Channel, inteimediate 

 between the latter and the Zebra Channel. 



There is reason to believe that the growth of the banks and the silting up 

 of part of the Rock Channel have been much promoted by the abstraction 

 of area which has taken place for dock purposes ; nor is this surprising when 

 we find the extent of this abstraction, and the important part of the river, 

 especially in relation to the Rock Channel, where it has been made. 



Between 1846 and 1859, or in six years, it seems that as much as 500 

 acres have been enclosed for the dock-works of Liverpool and Birkenhead, 

 and the result apparently confirms the correctness of the principle laid down 

 by Mr. Whidbey and other eminent engineers who have reported upon the 

 river, as indicating the consequence of diminishing the scouring power of 

 the last of the flood and the first of the ebb, the situations of the abstractions 

 referred to being in parts of the river which are occupied by those portions 

 of the tidal waters. 



It appears from Mr. Boult's researches, that the change of direction in the 

 channels is not so much the result of the direction of the dock walls as of 

 alterations in the size and position of the sand-banks ; alterations which seem 

 to be due to the permanent loss of scouring power, by abstraction of tidal 

 area ; to the temporary increase of that loss from drought ; to the temporary 

 accession of scouring power from freshes; and to the drifts of sand by the . 

 winds to which the bay is peculiarly exposed, and which are the prevailing 

 winds on this part of the coast. The extent of this sand-drift is so great, 

 that, since Collins's survey, the eastern shore of the estuary appears to have 

 advanced westward as much as one-half the width of the northern channel, 

 or about 1000 yards. 



It is possible that the deterioration of the Rock Channel is to be ascribed, 

 in part, to the erection of the new north wall at Liverpool. It is built on 

 the Bootle shore, almost immediately opposite the junction of that channel 

 with the northern channel, and directly across the direction of the tidal 

 stream in the Rock Channel. Therefore, the flood-stream entering the river 

 by that channel is suddenly checked by this upright wall, and is deprived of 

 the space formerly allowed by the sloping Bootle shore for gradually changing 

 its direction into that of the main course of the river and the northern 

 channel. 



It was observed by Messrs. Whidbey, Chapman, and Rennie, in their 

 Report to the Corporation of Liverpool in 1822, that " all channels through 

 which water flows must be of a magnitude proportionate to the quantity 

 ^rhich passes them, and anv increase or diminution of that quantity will 



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