The newly discovered elementary particles

Written especially for Electrical, Engineering; based upon an address delivered before the communication group of the A.I.E.E. New York Section, New York, N. Y., April 23, 1935. During the 3 years following the discovery of heavy hydrogen in the latter part of 1931, 4 additional elementary particles of matter lighter than the alpha particle (nucleus of the ordinary helium atom) have been discovered where only 2 were known previously. This is considered extraordinary even for the present rapid pace of physics which sometimes requires physicists to revise their fundamental concepts of matter almost overnight. These 5 newly discovered particles formed the subject matter of a highly interesting and instructive address delivered recently by Doctor Darrow at a meeting of the Institute´s New York Section; the essential substance of this illuminating address is presented herewith.