This cloud-chamber photograph, showing the track of a positively charged particle of electronic mass slowed down by passing upward through a lead plate, was among the earliest evidence of the existence of the positron adduced by C.D. Anderson (1932). The promotion of physics at Berkeley may be illustrated by the main line of work of Millikan's research group around 1930. The line was study of "cosmic rays," the "birth cries of the universe" (both phrases coined by Millikan); its financial backing, local resources and the Carnegie Institution of Washington; its most elaborate method, the examination of tracks left by the rays as they crossed a big cloud chamber exposed to a strong magnetic field.