The unassisted efforts of nature have hitherto maintained the navigable channels of the Mersey, so that the conditions of navigation remain practically uniform. The bar, however, is gradually moving in a seaward direction, while maintaining its general form and characteristics. In Liverpool Bay there is a great range of tide, which insures a depth of at least 30 feet over the bar once in every twelve hours, even on the lowest neaps. Some two or three million cubic yards of upland water every twelve hours are discharged into the estuary, chiefly by the Mersey and the Weaver, which, with 710 million cubic yards on a high spring tide, maintains the normal capacity of the estuary, and counteracts the process of silting. Some 17,300 acres of a deposit of sand in the estuary are above the low-water mark. Through this the upland water forms and maintains a channel in its course to the sea, and any serious exclusion of this tidal water would be likely to so far injure the sea channels as to interfere with the trade and shipping of the port. The Mersey is the outlet for several important canal navigations, including the Weaver Navigation Canal, near Weston Point, the Bridgwater Canal at Runcorn, the Sankey Canal at Widnes, the Shropshire Union Canal at Ellesmere, the Leeds and Liverpool Canal at the Docks, and the Manchester Ship Canal, now under construction, at Eastham. The position of these several canals in relation to the river may be traced in a map accompanying a paper read by Mr. Lyster, the engineer, before the Institution of Naval Architects. These canals are important factors in assisting the growth of the trade of the Mersey. The Leeds and Liverpool is, however, the only canal that has a direct connection with the Liverpool Docks. By this canal Liverpool has water communication with the important town of Leeds, and thence, by the Aire and Calder Canal, with Hull and the other ports on the Humber. By the Shropshire Union Canals the Mersey is connected with the network of canals in the Midland Counties and with the River Severn. In Camden’s time Liverpool must have been a very obscure place. The author of ‘Britannia’ dismisses it almost in a sentence, observing that “from Warrington, the River Mersey, spreading abroad, and straightwaies drawing in himselfe again, with a wide and open outlet, very commodious for merchandise, entereth into the Irish Sea, where Litherpoole, called in the elder ages Lipen-poole, common Lirpoole, is seated, so named, as it is thought, of the water spreading itself in manner of a poole.”