- Sir William,1832–1919, English chemist and physicist: discovered the element thallium and the cathode ray.
- Sir William. 1832–1919, English chemist and physicist: he investigated the properties of cathode rays and invented a type of radiometer and the lens named after him
- British chemist and physicist who discovered thallium in 1861 and invented the radiometer (1873-76). He also developed the Crookes tube, a modified vacuum tube that was later used by W.C. Roentgen and J.J. Thomson in experiments that led to the discovery of x-rays and the electron, respectively.