296 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1931 



Thus our assault on atoms has broken down the outer fortifications. 

 We feel that we know the fundamental rules according to which the 

 outer part of the atom is built. The appearance and properties of 

 the electron atmosphere are rather familiar. Yet that inner citadel, 

 the atomic nucleus, remains unconquered, and we have reason to 

 believe that within this citadel is secreted a great treasure. Its cap- 

 ture may form the main objective of the physicists' next great drive. 



