Sir William Crookes was born June 17, 1832 in London, England and died April 4, 1919. He is was British chemist known for his discovery of the element thallium and for his cathode-ray studies. William attended the Royal College of Chemistry in London. This lead him to be ,in 1854, the superintendent of the meteorological department at Radcliffe Observatory in Oxford. Then in 1856 he inherited a fortune from his father and dedicated himself to scientific work at his private laboratory in London. During his research he discovered the element thallium and cathode rays which contributed to the development of the atomic theory. Sir William Crookes invented the cathode ray tube in which he discovered cathode rays. A cathode ray tube is shaped like a bottle and has the air vacuumed out. Then, there are two metal plates that a power source is connected to. This power source creates a cathode ray. The ray flows in a strait line to the end of the tube. William's cathode tube helped others make further discoveries that eventually created the atomic theory (the theory that all matter is made up of tiny indivisible particles). This was done when J.J.Thomson placed a positive plate on one side and a negative plate on the other causing the cathode ray to bend towards the positive plate. This indicated that the cathode ray is negatively charged because opposite charges are attracted to one another. These negatively charged particles are called electrons. The discovery of electrons then proved that all matter is made up of tiny indivisible particles called atoms.