text: Daltons atomic theory remained controversial throughout the 19th century. Whilst the Law of definite proportion was accepted, the hypothesis that this was due to atoms was not so widely accepted. For example, in 1826 when Sir Humphry Davy presented Dalton the Royal Medal from the Royal Society, Davy said that the theory only became useful when the atomic conjecture was ignored. English chemist Sir Benjamin Collins Brodie in 1866 published the first part of his Calculus of Chemical Operations as a non-atomic alternative to the atomic theory. He described atomic theory as a Thoroughly materialistic bit of joiners work. English chemist Alexander Williamson used his Presidential Address to the London Chemical Society in 1869 to defend the atomic theory against its critics and doubters. This in turn led to further meetings at which the positivists again attacked the supposition that there were atoms. The matter was finally resolved in Daltons favour in the early 20th century with the rise of atomic physics.