THE RIVER MERSEY. 11 



the purpose of effecting a scour ; the water from the highest parts having 

 to run through the greatest length of the navigable channels in its passage 

 to Liverpool, and afterwards through the sea channels at a period when the 

 tidal waters have considerably ebbed, and when those channels are narrowed 

 within the banks that enclose them. 



The centre of Liverpool is about three and a half miles above the mouth 

 of the river, while Runcorn is nearly twenty miles ; the value, therefore, of 

 the tide at Runcorn compared with that at Liverpool (taking it only at the 

 relative distance between those places), is nearly as 5 to 1 ; but it is also 

 beneficial in a manifold degree in consequence of its operating so much 

 more powerfully to scour the bed of the channels at Liverpool and the sea 

 channels than any water can do which is discharged from situations nearer 

 the mouth of the river in the early parts of the ebb tide. Another circum- 

 stance may be cited in favour of preserving the tidal waters at Runcorn, 

 and particularly upon the flat stones near to the level of high water. The 

 fact has been proved by Mr. Giles, that the spring tides actually rise one" foot 

 and a half higher at Runcorn than at Liverpool, consequently any enclosure 

 of such shores at Runcorn must be exceedingly injurious. 



Too much vigilance therefore cannot be exercised in preserving the tidal 

 waters at Runcorn, and also in having it discharged by the natural ebb of 

 the tide. 



Report dated 30th January, 1827 (No. 2). — Mr. R. Stevenson states, as a 

 principle which ought to regulate all operations upon the banks of rivers, 

 that backwaters, are essential to the preservation of such rivers in a navi- 

 gable state ; and with regard to the Mersey, he is of opinion that the great 

 influx and reflux of tides into this estuary every twelve hours is what alone 

 preserves the Horse and Formby Channels in their present navigable state. 

 To the preservation of these channels all the arguments relating to the back- 

 water resolve themselves. An alteration in the depth or direction of these 

 channels might be attended with consequences most serious to Liverpool, 

 encumbered as its entrance is with sand-banks of a great extent. 



He also recommends that the jurisdiction of the conservators should 

 follow the high-water mark in all its gambols, though trenching sometimes 

 upon one side of the estuary and sometimes upon the other, and that they 

 should take the most prompt cognizance of all works undertaken upon the 

 ebb, or between the points of high and low water. He conceives that a 

 distinction should be made between works intended for the legitimate pur- 

 pose of navigation, and those which have for their object the acquirement 

 of firm ground at the expense of the backwaters of the river. 



Report dated 2>\st January, 1827 (No. 2). — Messrs. Walker and Mylne 

 state that the Mersey is only deeper at Liverpool than at Warrington, be- 

 cause the greater quantity of water at Liverpool requires a greater area to 

 pass it. If the tide was excluded, the Mersey at Liverpool would by the de- 

 posit of matter brought down from the interior soon diminish to the same size 

 as at Warrington, and the entrance from the sea would soon sand up, leaving 

 space sufficient only to pass the water of the river in this diminished state. 



Report dated 21 th September, 1836 (No. 2*). — Captain Denham says, the 

 progress of Pluckington Bank, since 1828, has been a horizontal increase 

 of 210 yards abreast of Brunswick Basin, abreast of King's Dock 123 yards, 

 and abreast of Duke's Dock only 40 yards. Its respective elevations he 

 cannot quote between these dates, but since 1834< he finds it grown up one 

 foot off Brunswick Dock, two feet off Brunswick Basin, three feet off Duke's 

 * Reprinted at length in No. 5 herewith. 



