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Ray Bombardment Cosmic rays, which Dr. Millikan believes are superpowerful gamma rays released when protons & electrons combine to form elements are everywhere on earth. They are invisible, powerful, penetrate almost anything. By utilizing their ubiquity Dr. Carl D. Anderson, Dr. Millikan's assistant at the California Institute of Technology, made them disrupt an atom's nucleus, took photo-graphs of the process. Between the poles of an electromagnet he placed a Wilson cloud-chamber apparatus—a cylinder with a piston, filled with moisture-laden air. When the piston is suddenly withdrawn the air expands, forms fog. If electric particles are moving in the cylinder the fog forms first on them, making their path visible. Dr. Anderson put nitrogen into his cylinder, exposed a bit of radium, withdrew the piston, flashed a light. He saw lines of tiny water droplets curving away from a common point. In one direction moved protons, showing a clear path. In the other direction went the electrons, their paths much fainter. From the curvature he calculated their speeds—93,000 mi. per second for the protons, 186,000 mi. per second for the electrons. To produce such speeds 50,000,000 volts energy is needed, so Dr. Anderson concluded that alpha particles from the radium (5,000,000 volts) could not have done it, that it must have been done by the cosmic ray. Electrons released by the alpha particles moved much more slowly, left a track almost straight. Dr. Anderson took 1,100 photographs, got eleven good ones. These Dr. Millikan proudly showed to scientists at Columbia University last fortnight.