182 THE ROYAL SOCIETY OF CANADA 



Using Moseley's relation — 



for N = 82, ^a=l-72Xl0 19 

 N = 83, ^a = l-75Xl0 19 



The agreement between the calculated and the experimental 

 frequency in the case of radium B suggests that the more penetrating 

 rays of radium belong to the K series. In the case of radium C 

 however, the observed frequencies are so much greater (the radiation 

 consisting of three lines with frequencies = 2-6lXl0 19 , 3-03 X 10 19 , 

 and 4-22 X 10 19 ) that it is evident that the 7 rays of Ra C cannot 

 belong to the K series of that element. 



Rutherford and Andrade consider that these rays belong to yet 

 another series, which for convenience they have called the H series. 



We know that a /3 ray must have energy E, approximately 

 = hv to excite X rays of frequency v, h being Planck's constant 

 6-55 X 10 -27 erg. sec, and further that Xrays of frequency ,J can 

 excite /3 rays of energy E approximately = hv. 



Applying the relation E = hy to the line of radium C spectrum 

 with the greatest frequency, we find that a /3 ray must have a speed 

 corresponding to a potential drop of 177,000 volts before it can excite 

 this radiation. As Rutherford and Andrade state, this is not beyond 

 the possibility of experiment with a suitable X ray tube, so that it 

 ought to be possible to observe the H series of characteristic radiations 

 by applying a sufficiently high voltage say 200,000 to an X ray tube 

 in which a heavy element like platinum forms the anticathode. 

 Radium E, however, if intense enough gives one a more convenient 

 source of high speed /3 rays than the X ray tube, the /3 rays varying 

 in speed from 2-72 to 1-50 X 10 10 cms. per sec, the average speed 

 being 2-40 X 10 10 cms. per second, these rays corresponding to a po- 

 tential drop of about 300,000 volts. The fastest rays correspond 

 to a drop of 600,000 volts. 



Some time ago the writer 1 examined the properties of 7 rays 

 excited in different materials by these /3 rays, particularly of the 7 

 rays excited in lead, and below an account is given of the absorption 

 of the 7 rays excited in lead, which shows that rays of the H series 

 are not excited in the lead. The source of /3 rays, a very active 

 specimen of radium (D + E + F) was placed between two sheets of India 

 paper, and then between two lead sheets 0- 1 mm. thick in which the 

 7 rays were excited. To absorb any /3 rays issuing from the lead, a 

 plate of graphite 5 mm. thick was placed above the upper lead plate. 

 The preparation was placed about 3 cms. below an electroscope, 

 t he bottom of which consisted of aluminiu m 1-25 mm. thick . Th e 



^ray, Proc. Roy. Soc. 1911, A vol. 85, p. 121; 1912, A vol. 86, p. 513; 1912, 

 A vol. 87 p. 489. 



