The AtomIn the spring of 1897 JJ Thomson demonstrated that the beam of luminous matter in a cathode ray tube was not formed by light waves, as "the almost unanimous opinion of German physicists" believed . Rather, cathode rays were negatively charged particles that boiled away from the negative cathode and were attracted to the positive anode. These particles could be deflected by an electric field and bent into curved trajectories by a magnetic field. They were much lighter than hydrogen atoms and were identical "whatever gas the discharge passes through" if the gas was introduced into the tube. Since they were lighter than the lightest known type of matter and identical regardless of the type of matter from which they arose, it followed that they must be a fundamental constituent part of matter, and if they were a part, then there must be a whole. The real physical electron implied a real physical atom: the particulate theory of matter was therefore convincingly justified for the first time by physical experiments. They sang the hit at the Cavendish annual dinner. Armed with the electron and knowing from other experiments that what remained when electrons were stripped away from an atom was much more massive than the positively charged remainder, Thomson continued over the next decade to develop a model of the atom that came to be called the "plum pudding". Thomson's atom, "a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification" like raisins in a pudding, was a hybrid: particulate electrons and diffuse remnant. It served the useful purpose of mathematically demonstrating that electrons could be arranged in asstable configurations within an atom, and that mathematically stable arrangements could explain the similarities and regularities between chemical elements shown by the periodic table of elements. It was becoming clear that electrons were responsible for the chemical affinities between elements, that chemistry was ultimately electrical. Thomson nearly discovered X-rays in 1884. He was not as unfortunate in legend as the Oxford physicist Frederick Smith, who discovered that photographic plates were stored near a cathode. The ray tubes may have fogged up and they simply told his assistant to move them to another place. Thomson noticed that the glass tube held "at a distance of a few feet from the discharge tube" fluoresces just as the wall of the tube itself did when bombarded with cathode rays, but he was too intent on studying the rays themselves to look for any the cause. Rontgen isolated the effect by covering his cathode ray tube with black paper. When a nearby screen of fluorescent material continued to glow, he realized that whatever was causing the...