EXPLORING THE ATOM 



per second waves powerful enough to drive rela- 

 tively large particles of matter before them, must 

 be in itself a center of energy of astounding power, 

 notwithstanding the incomprehensible minuteness of 

 its size. 



All these studies of the different manifestations 

 of energy point in the direction of the atom, and 

 give us more or less vague estimates of the activities 

 of this tiny structure. It remained for a new line 

 of investigation to reveal the atom itself. The new 

 observations came about through the discovery of 

 substances having curious properties hitherto un- 

 suspected but now familiar to everyone under the 

 name of radioactivity. 



A NEW TYPE OF RADIATION 



The initial discovery of a radioactive substance 

 was made by the French physicist Becquerel, through 

 the accidental observation of the effect of the chemi- 

 cal called uranium on a photographic plate. The 

 discovery of other radioactive substances, including 

 radium, by Professor and Mme. Curie, quickly fol- 

 lowed, and the strange new properties were studied 

 by many workers, chief among whom is Professor 

 Ernest Rutherford, now of Manchester University. 



The essential phonomena of radioactivity consist in 

 the giving off of rays capable of affecting the photo- 

 graphic plate and of penetrating opaque substances. 

 The radiation comprises at least three different types 

 of rays, which have been named alpha, beta, and 

 gamma rays. It is now known that the alpha rays 

 consist of relatively heavy particles which are in r$- 



