Arthur Stanley Williams (1861-1938), British amateur astronomer. Williams was a solicitor, carrying out his astronomical work in his spare time. Most of Williams's observations were of the planet Jupiter, and from 1898 he began naming the cloud belts and zones . His most famous paper is 'Periodic Variations in the Colours of the two Equatorial Belts of Jupiter' (1899). He observed spots on Saturn and concluded that the Martian 'canals' were illusions. He was awarded the Jackson-Gwilt Medal of the Royal Astronomical Society in 1923. He was a keen sailor, winning the Challenge Cup in 1920, and left instructions to be buried at sea. Craters on the Moon and Mars are named in his honour.