﻿Disintegration of Elements by a Particles. 421 



a field due to an exciting current of 4 amps. ; the corre- 

 sponding ratio was 2*1. 



When the source had decayed to a small fraction of its 

 initial value, the aluminium foil over the source was removed 

 and a thin sheet of paraffin wax put in its place. The mica 

 sheet in front of the ZnS screen was replaced by a sheet of 

 3'4 cm. stopping-power, making the total absorption equi- 

 valent to 16 cm. of air. The scintillations observed on the 

 screen were now due to H particles ejected from the paraffin 

 wax of ranges between 16 cm. and 29 cm., the average range 

 being about 22 cm. The ratio of the numbers of scintillations 

 for — and + fields was determined for an exciting current of 

 4 amps, and found to be 3*2. 



It appears from these results that the long-range particles 

 from aluminium of average range 45 cm. were less deflected 

 by the same magnetic field than H particles of average range 

 22 cm. ; and that in the magnetic field due to a current of 

 6 aiups.^ which was 1*34 times the intensity of the field due 

 to 4 amps., they were more deflected than were the H particles 

 in the latter field. To a first approximation we may say that 

 the value of mvje for particles from aluminium of range 45 cm. 

 is 1'23 times greater than that for H particles of range 22 cm. 

 This result is clearly consistent with the view that the particles 

 from aluminium are H nuclei moving with high velocity; 

 for, assuming that the range of the H particle is pro- 

 portional to the cube of its velocity, the velocity of a particle 

 of range 45 cm. is 1*27 times that of a particle of 22 cm. 

 range. 



These experiments show, therefore, that the particles from 

 aluminium carry a positive charge and are deflected in a 

 magnetic field to the degree to be anticipated if they are 

 hydrogen nuclei moving with a velocity estimated from their 

 range. While there can be little doubt that the particles 

 are hydrogen nuclei, it is very difficult to prove this point 

 definitely without an actual determination of the velocity and 

 value of e/m of the particles. Our knowledge of the relation 

 between the range and velocity of complex charged particles 

 is too indefinite for purposes of calculation. On the other 

 hand, if we assume, as seems a priori probable, that the 

 ejected particle is the free nucleus of an atom, it is possible 

 to show with some confidence that only a particle of mass 1 

 and charge 1 can fit the experimental results. 



Additional evidence as to the value of mvje of the particles 

 from aluminium was obtained by comparing their magnetic 

 deflexion with that of the a particles of S'Q cm. range emitted 

 by thorium C. In this experiment the source R was a very 



