7 fiermions emitted by tJie Alkali Sulphates. 'J 87 



respectively, and at the end '489 and '485. The mean of 

 these values o£ z is "483 cm. 



The observations taken immediately after the lithium 

 sulphate was placed on the strip are exhibited in fig. 2. Here 

 again we have the result o£ two determinations taken im- 

 mediately after one another, for each direction of the magnetic 

 field, the first being shown thus : ©, the second thus : x . 

 As before, the corresponding curves are not quite identical 

 but the displacement of the maximum is the same for each 

 pair. It is slightly less than that for platinum, indicating 

 that the ions emitted by fresh lithium sulphate are slightly 

 heavier than those emitted by that metal. The curves are 

 also rather broader than those for platinum. Immediately 

 before this series of measurements was made the value of z 

 was measured and found to be *485 cm. These curves have 

 only one maximum, showing either that the ions are all of 

 one kind, or at any rate that the value of e/m for the different 

 kinds, if more than one, does not vary enough for them to be 

 separated by the magnetic field used. 



The next curve (tig. 3) shows the effect of heating the 

 lithium sulphate continuously for twelve hours. The right 

 and left hand curves, points thus : 0, are those obtained 

 when the magnetic field is applied ; the central curve, points 

 thus : x , is what is obtained in the absence of the magnetic 

 field. We see that the curves obtained in the presence of 

 the magnetic field are now more complex than before. In- 

 stead of having a single maximum we now have two maxima 

 separated by a minimum. The obvious explanation of this 

 is that there are now two kinds of ions present which 'are 

 differently deflected by the magnetic field. That this is the 

 correct explanation is shown by the curve obtained in the 

 absence of the magnetic field. This possesses only one 

 maximum, and is in all respects similar to those obtained 

 earlier, in the magnetic field. The shape of this curve 

 entirely precludes the possibility that the humps are due to 

 some irregularity which has developed in the distribution of 

 the salt along the strip. 



The distance between the two inner humps, corresponding 

 to the heavier particles, is about the same as that given by a 

 new platinum wire or a fresh specimen of lithium sulphate ; 

 wmereas the distance between the two outer humps is very 

 much greater and corresponds to ions of much smaller mass. 

 The value of z in this experiment was *477 cm. 



As the heating is continued it is found that the outer hump 

 grows whilst the inner hump diminishes. After 30 hours 

 heating the outer humps were much bigger than the inner 



3T 2 



