Editing Imperial units (section)

== Natural equivalents ==
The 1824 Act of Parliament defined the yard and pound by reference to the [[prototype]] standards, and it also defined the values of certain [[physical constants]], to make provision for re-creation of the standards if they were to be damaged. For the yard, the length of a [[pendulum]] beating [[second]]s at the latitude of Greenwich at [[mean sea level]] {{lang|la|in vacuo}} was defined as {{val|39.1393}} inches. For the pound, the mass of a cubic inch of distilled water at an [[atmospheric pressure]] of 30 [[inches of mercury]] and a temperature of 62° [[Fahrenheit]] was defined as 252.458 grains, with there being 7,000 grains per pound.<ref name="google339" />

Following the destruction of the original prototypes in the [[Burning of Parliament|1834 Houses of Parliament fire]], it proved impossible to recreate the standards from these definitions, and a new [[Weights and Measures Act 1855]] was passed which permitted the recreation of the prototypes from recognized [[Standard (metrology)|secondary standards]].<ref name="Britain1855" />