C. Northcote Parkinson and journalist Ann Fry (1921–1983), with whom he had two sons and a daughter. In 1958, while still in Singapore, he published his most famous work, "Parkinson's Law", which expanded upon a humorous article that he had published in the "Economist" magazine in November 1955, satirising government bureaucracies. The 120-page book of short studies, published in the United States and then in Britain, was illustrated by Osbert Lancaster and became an instant best seller. It explained the inevitability of bureaucratic expansion, arguing that 'work expands to fill the time available for its completion'. Typical of his satire and cynical humour,
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