HIGH VOLTAGE — COMPTON 259 



would just compensate gravity. This would be an extremely high 

 voltage such as could be obtained onl}^ if the apparatus were oper- 

 ating in a vacuum, and, in fact, Dr. Swann suggests that it may be 

 operated in this manner. 



With this historic survey of electrostatic generators, let me noAv 

 return to the text of my address, " Necessity is the mother of inven- 

 tion." Until very recently there was no compelling need to force 

 physicists to seek ever higher and higher voltages in electrical gen- 

 erating devices. Their needs were met by existing devices of the 

 electromagnetic type. Within the past dozen years, however, it has 

 become evident that a whole new range of fundamental investiga- 

 tion into the properties of atoms will be opened up by a suitable 

 source of high potentials. 



This new inducement ma}^ be said to have arisen with Rutherford's 

 discovery that it is possible to transmute one chemical element into 

 another by bombarding it with the fast electrified particles known 

 as alpha particles, which are spontaneously given off by radioactive 

 materials in tlie process of their disintegration. These brilliant ex- 

 periments opened up a whole range of new explorations into the 

 structure of the atomic nucleus and stimulated the imagination of 

 scientists in regard to what might be done if only they had available 

 some more powerful and better controllable source of high-speed 

 missiles to shoot at the atomic nuclei. Tlie alpha particles from 

 radium do have tremendous velocities, but they are relatively few in 

 number, and all the radium that could conceivably be gathered to- 

 gether in the world would not produce a stream of electrified parti- 

 cles comparable to that which can be obtained in an ordinary 

 discharge of electricity through a vacuum tube. If only the voltage 

 as applied to a vacuum tube could be made high enough to give the 

 ions in a vacuum tube speeds comparable with or even exceeding 

 those of alpha particles from radium, what a powerful attack could 

 be made upon the nucleus. Not only could particles in billionfold 

 larger numbers be used, but dilfei-ent kinds of particles could be 

 tried, such as hydrogen nuclei, helium nuclei, lithium nuclei, neon 

 nuclei, and so forth, and these could be given any desired speed up 

 to the maximum limit determined by the highest voltage available. 

 So for the past dozen years, tlioughts of scientists have again been 

 turned to means for produc ing ever and ever higher voltages. 



It was to this end that the million-volt installation at the Cali- 

 fornia Institute of Technology was designed. It was also to this 

 end that a system of high-potential transformers and condensers 

 was built by Cockcroft and Walton in Cambridge, with which they 

 were the first successfully to disintegrate atoms by means of elec- 

 trified particles produced from an artificial source and speeded up 



72774—36 18 



