Teachers & Group Leaders

Gauging Rod

Key Stage 2
60 Minutes
Up to 20 children


A gauging rod is a calibrated pole that was used in the working days of canals to measure how low in the water a boat was lying. Printed tables were kept at toll offices showing the unladen weight, and depth in the water, of all the boats using that canal. Tolls were charged according to weight of cargo. By comparing the unladen position in the water with the laden position, measured with the gauging rod, the toll clerk could tell how much weight of cargo was on board the boat and therefore how much the toll would be. The museum has a gauging rod in position alongside its centerpiece exhibit, the narrowboat Coronis. This workshop extends the knowledge of floating & sinking that children have already acquired at Key Stage One. It introduces the concepts of gravity & upthrust, investigates the effect of shape on buoyancy, and how a gauging rod was used by making models of them both.

National Curriculum


  • Calculations and problem solving (all years)


  • Explain that unsupported objects fall towards the Earth because of the force of gravity acting between the Earth and the falling object (Y5)

Learning Objectives

  • To understand the meaning of the words float and sink
  • To introduce the concepts of gravity & upthrust
  • To explore the influence of shape on the buoyancy on a body of plasticine of a a given mass
  • To find out how a gauging rod was used to measure the relative balance of upthrust and gravity in testing how laden a narrow boat was


The delivery of this session can be adapted to a range of abilities – please notify the Education Officer of any specific needs.