New prototypes were subsequently created to replace the items lost in the fire, among them a new "yardstick" ruler in 1855, and with it a new formal definition of the yard.
[2][3] There were two factors that influenced the order: for one, the imperial standard yard of 1855 had been found to be unstable and shortening by measurable amounts.
In the United Kingdom, a similar situation developed with the Weights and Measures Act 1897 legalizing the metric system,[4] and Order in Council 411 (1898) defining the meter and kilogram in terms of the yard and pound.
[6] In the 1890s, Albert Michelson began conducting experiments in interferometry that led in 1903 to demonstrating the feasibility of using light waves as units of linear measurement.
In 1908, two teams of researchers, one led by Michelson, defined the length of the international prototype meter in terms of light waves.
[16] The UK adopted the international yard and pound for all purposes through the Weights and Measures Act 1963, effective 1 January 1964.