Henry Kater’s 40 inch standard bar

Made in England, c.1835.

Why is this bar triangular, with two gold plugs in it? In 1820 British army officer Captain Henry Kater made precise measurements (to a millionth of an inch) to compare this bar with others, with the aim of creating an official length standard for the British Empire. He chose a triangular rather than flat bar to minimise thermal expansion. He chose gold for the plugs because it is soft and inert, and he used a microscope to position the lines he inscribed on the plugs 40 inches apart.



Object No.


Physical Description

A triangular, solid metal, 40 inch line bar stored in a polished timber case with a hinged lid. There is also an associated stand with the line bar. The stand is made up of three pieces, a rectangular metal base that supports two metal cradles.



There is no makers mark on this standard bar.





This standard measure was used by Captain Henry Kater in the adjustment of the imperial standard measures of Great Britain.

Kater worked along side Sir Joseph Banks and Thomas Young to experiment using measures and weights, and devise methods of taking accurate measurements. Their work significantly influenced the Weights and Measures Act of 1824, which introduced the new British imperial standards for measurements of lengths and weights.

Henry Kater's son, Henry Herman Kater, arrived in Australia in 1839. He had inherited many of his father's possessions after the death of his brother Edward, and this standard bar was one of them. He donated most of these objects to Sydney University and to Sydney Observatory.

This standard bar was presented to Sydney Observatory by Henry Herman Kater in 1873.

Macmillan, D. S., The Kater family, 1750-1965, The Kater family?, Sydney, 1966
Holland, J., 'Pioneer of Precision; Captain Henry Kater, FRS', http://www.usyd.edu.au/museums/whatson/exhibitions/kater1.shtml
Lomb, N., 'Earnshaw's Excellent Timekeepers', in Davison, G., Webber, K., 'Yesterday's Tomorrows; the Powerhouse Museum and its precursors 1880-2005', Powerhouse Publishing, 2005
Forwarded to H. M. Secretary of State by Despatch, No. 141, 1847, Federation and Meteorology, http://www.austehc.unimelb.edu.au/fam/1541.html


Kater, Henry 1820-1835

Cite this Object


Henry Kater's 40 inch standard bar 2018, Museum of Applied Arts & Sciences, accessed 17 November 2018, <https://ma.as/259027>


{{cite web |url=https://ma.as/259027 |title=Henry Kater's 40 inch standard bar |author=Museum of Applied Arts & Sciences |access-date=17 November 2018 |publisher=Museum of Applied Arts & Sciences, Australia}}
This object is currently on display in Store 4 at the Museums Discovery Centre.


This object record is currently incomplete. Other information may exist in a non-digital form. The Museum continues to update and add new research to collection records.

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