Connexion between /3 and 7 Ray Spectra. 317 



expected for the 7 radiation reflected at 1° 24'. With the 

 exception of lines 1 and 11, there appears very little evidence 

 of the unit of energy corresponding to the strong reflexion 

 line at about 1° 40', the energy of which should be about 

 •750. There is another unit, however, '553 which agrees 

 fairly well with a number of lines. The observed 7-ray line 

 nearest to this value is reflected at 2° 20' of energy -537, but 

 the difference in the observed and calculated energies is more 

 than two per cent. Possibly the unit may be 1*10 corre- 

 sponding to the 1° 10' line. 



It will be observed that several of the lines are in 

 approximate accord with multiples of different units calcu- 

 lated from the frequencies of observed lines. This will be 

 seen by comparison of the above table with the energies for 

 frequencies given on p. 313. 



Apart from the group of slow velocity lines and lines 2 

 and 6, the agreement between observed and calculated 

 energies is fair, but is not sufficiently definite to draw certain 

 deductions as to the origin o£ the individual lines in the 

 spectrum. 



There is one interesting point which should be mentioned 

 here. Danysz * determined the velocities of the slow velocity 

 groups of /3 rays from radium D, and found them to be quite 

 different from the corresponding groups of /3 rays (11-16) 

 in the spectrum of radium B, although the actual numerical 

 differences between the energies of the corresponding lines 

 were approximately the same for the two substances. Now 

 the general evidence indicates that radium B and radium D, 

 although of different atomic weights, have identical general 

 chemical properties, and would be expected to give the same 

 7-ray spectra, and also the same type of primary /3 rays. 

 It has been pointed out earlier in this paper that the observed 

 differences in /3 and 7 ray spectra may possibly be ascribed 

 to the different conditions of excitation of the 7 rays in the 

 atom in the two cases due to the expulsion of the /9 particle 

 from the nucleus in a different direction with regard to the 

 structure of the atom. If the latter point of view is correct, 

 we should anticipate that the energies of the groups of 

 ft rays from radium D should be expressed in terms of some 

 of the frequencies in the 7 rays of radium B. 



The energies observed by Danysz are *309, *311, '435, 

 •468 X 10 13 e. Two of these agree well with the values of 

 the energies *312, *469xl0 13 <?, calculated for the lines of 

 radium B reflected from rocksalt at angles of 4° and 2° 40'. 

 The line 2° 51' of energy '438 was observed on one or two 

 * Le Radium, x. p. 5 (1913). 



