Written for Brought to Light by: Catherine Lea. Research Group: Lauren Koopowitz, Amy Forester, Isaac Hutchins, Catherine Lea.
British made Polar Planiameter. Scientific instrument. Housed in black plastic or bakelite case, in cardboard box. Maker: Allbrit. Includes 'Instructions for use of the Allbrit Planimeter' booklet and 'Supplementary Instructions for the Allbrit Polar Plan.
The Polar Planimeter was invented in 1854 by Swiss mathematician Jacob Amsler (1823 - 1912). It uses Green's Theorem (vector calculus) to calculate the area inside an irregular two-dimensional shape. Planimeters have been used extensively in engineering but have also been used in a wide range of other fields including geology, physics, biology, and psychology. This example is a polar planimeter and was made in London Circa. 1951. It was most likely used within the school of geology during the 1950s and 60s. The term 'polar' relates to its utilisation of polar co-ordinates (radius, angle) instead of cartesian co-ordinates (x, y).
The Planimeter belongs to a family of measuring tools knowns as integrators and is used to determine the area inside an irregular shape. This item is a complete set including a user guide and comes in its own Bakelite storage box. Constructed from metal and plastic/resin, the planimeter consists of the following components: tracer aim, carriage, measuring wheel with vernier, tracer point, pole arm, calibrating ruler and magnifying lens. Once it has been assembled as per the included user guide. The operator moves the tracer point along the boundary of the shape to be measured. On completion, the dials on the rollers indicate the area inside the shape. We believe that this planimeter was used by Eric Rudd, the University’s first head of Economic Geology. Also, it is known that Douglas Mawson had a keen interest in cartography and it is highly likely that he would also used a similar (but earlier model) planimeter in his work. Additionally, it is assumed that this item was used in the geology department based on its discovery location in the Mawson Building. However, it is possible that it may have initially come from another department such as engineering. Scholarly literature from the 1880’s to 1950s indicates that planimeters were used in a wide variety of fields including mechanical and Civil Engineering, Physics, Biology and Psychology.
