RADIUM AND THE ELECTRON 
RUTHERFORD. 208 
From the above hurried survey of the progress of atomic physics 
it will be seen that the investigations of the past twenty-five years 
have dealt mainly with three great outstanding problems, viz, the 
nature of electricity, the structure of the atom, and the nature of 
radiation. While great additions have been made to our knowledge 
of these questions leading to a much wider outlook, we can not but 
recognize that much still remains to be done before we are certain 
that we are building on a firm foundation for the future. Notwith- 
standing the prolonged halt during the war, the scientific outlook is 
one of good augury for the immediate future, and there is every 
prospect that the vigorous attack on these outstanding problems will 
be continued. 
