284 AUSTIN: APPARATUS FOR RADIOTELEGRAPHY 



positive rays is also a complex phenomenon, in which the emission 

 of a spectral line depends not only on the radiating atom but 

 also on the velocity of the atom or electron which excites the radia- 

 tion. One must therefore try to make the conditions of experi- 

 ment still simpler. 



Another phenomenon to which it may be possible to apply the 

 theory of quanta is the scintillation caused by the impact of a-rays 

 against a phosphorescent body. In a sense we have here an ele- 

 mentary operation because the light, which is emitted in one 

 scintillation is caused by a single a-particle. But the amount of 

 energy radiated in the scintillation is much larger than one quan- 

 tum and it seems that this energy does not come from a single 

 atom of the phosphorescent substance but from a great number of 

 atoms, all excited by the same a-particle. 



After this survey of the field we are thus compelled to admit 

 that for the moment we have no experiment which permits the 

 observation of a single quantum of energy. With light We can- 

 not hope to make such observations directly because more than 

 thirty quanta are necessary to be perceptible to the eye. In 

 Rontgen rays the element of energy is more than 1000 times larger 

 but here we have no instrument of observation as sensitive as 

 the tmman eye. 



It is therefore unavoidable that in the study of the quanta 

 theory we are confined to statistical methods, and these do not 

 give us a convincing interpretation in terms of physical fact. It 

 is only by applying the theory of quanta to many and widely 

 different phenomena that we can hope to find out the true physi- 

 cal explanation of this novel theory. On the other hand it is 

 evident that hardly more than the first steps have yet been taken 

 and that by far the greater part of the work still remains to be 

 done. 



RADIOTELEGRAPHY. — A Comparison of arc and spark send- 

 ing apparatus for radiotelegraphy . L, W. Austin, U. S. Naval 

 Radiotelegraphic Laboratory. 



It has been claimed by the users of continuous oscillations in 

 radiotelegraphy that these waves are less absorbed in passing 



