Observations on the most advantageous line of country through which a canal navigation may be carried, from Newcastle upon Tyne, or North Shields, towards Cumberland, &c with a proposal to extend collateral branches by the Pont and Blyth Rivers to Morpeth, the port of Blyth, &c. and pointing out the practicability of carrying a line of canal through the middle of Northumberland to Berwick upon Tweed