Toll Point - Gauging Point

Gauging Point

Canals were set up as commercial enterprises. The fee for using the canals was dependent on the type of cargo and its weight. Each boat had to have four (or, for some canal companies - Swansea, Glamorganshire, Oxford, six) gauging plates fitted to the hull at the "corners" of the boat - bow and stern at each side - indicating a measurement point and a boat serial number.

The boat was calibrated by measuring the height of the gunwales above water level at each corner with the boat unladen and then measured again when known weights had been loaded into the boat from an overhead gantry. These measurements were logged in toll-keeper's tables and copies sent to every toll office within the boat's trading range. At toll offices if a toll collector suspected an incorrect waybill (declared cargo) the height of the four corners of the boat were checked with a gauging stick and averaged to allow for uneven cargo loading. That boat's entry in the gauging table was used to determine the cargo weight. The toll fee was worked out from the weight and cargo type.

The fitting and calibration of gauging plates was done at a gauging station or indexing station. On the Birmingham Canal Navigations (BCN) Main Line the Smethwick Gauging Station near the Engine Arm Aqueduct was on an island, with a covered gantry in a centre channel where boats were loaded with weights, plated and calibrated. The channels either side allowed two-way traffic and possibly the collection of tolls. The buildings and equipment were demolished in the 1940s. Another BCN indexing station at Tipton survives. Here iron weights were loaded, four tons at a time. Other canal companies had stations at Etruria on the Trent and Mersey Canal and Northwich on the Weaver.

The gauging plates originally had scales showing the tonnage marked on them but around 1810 the method of using tables was implemented, often supplemented by a visible scale for quick checking. Boats were re-indexed every ten years as their wooden infrastructure became waterlogged and they ran lower in the water.