I know how the canal rays are produced. As I looked from wikipedia; "The process by which anode rays are formed in a gas discharge anode ray tube is as follows. When the high voltage is applied to the tube, its electric field accelerates the small number of ions (electrically charged atoms) always present in the gas, created by natural processes such as radioactivity. These collide with atoms of the gas, knocking electrons off of them and creating more positive ions. These ions and electrons in turn strike more atoms, creating more positive ions in a chain reaction. The positive ions are all attracted to the negative cathode, and some pass through the holes in the cathode. These are the anode rays." My question is, when did this explaination discovered? Did Goldstein offered this explanation when he discovered the canal rays, or somebody else did years later? One more question: How can we be so sure that the positive ions are +1, can't it collide with one more electron on its way and become +2?