Ministry of Defence Main Building (United Kingdom) each and cost £12,600. Similar figures representing "air" and "fire" were intended to be installed at the south end of the building, however these were never constructed. During the 1950s, building staff nicknamed the statues "Mr and Mrs Parkinson", after Cyril Northcote Parkinson, the Board of Trade civil servant who devised Parkinson's Law which states "work expands so as to fill the time available for its completion". More recently MOD staff refer to the statues as the "two fat ladies". The badge of the RAF is carved into stone columns either side of the southern entrance to the building, reflecting
Fermat's principle prefers the path such that there are other paths, arbitrarily nearby on either side, along which the ray would take almost exactly the same time to traverse. Fermat's principle can be used to describe the properties of light rays reflected off mirrors, refracted through different media, or undergoing total internal reflection. It follows mathematically from Huygens' principle (at the limit of small wavelength). Fermat's text "Analyse des réfractions" exploits the technique of adequality to derive Snell's law of refraction and the law of reflection. Fermat's principle has the same form as Hamilton's principle and it is the basis of Hamiltonian