Mr Thomson, Note on the nature of the carriers of Anode Rays 211 



in the ratio s/l to a/39, indicating that they were due to Li and K 

 respectively. On one plate a faint line appeared corresponding to 

 about 140 atomic weight which is probably due to iodine, the 

 accuracy being poor for large atomic weights. 



In order to confirm the interpretation of these lines an absolute 

 determination of ejm was made from measurements of the electric 

 and magnetic forces. Taking e/wi for the hydrogen atom as 9571 

 the measurements gave an atomic weight for the more d-eflected 

 lines of 6-9, assuming a single charge, thus confirming the theory 

 that they are due to single charged atoms of lithium. For accurate 

 work a better method -would be to use the apparatus, with an 

 ordinary anode and the aluminium plate as cathode, to give positive 

 rays, and use these to calibrate the plate ; it may even be possible 

 to get both anode and positive rays simultaneously. 



Owing probably to an irregularity in the electric field the lines 

 so far obtained are not very sharp, but one plate has been obtained 

 where the width of the line due to lithium is no larger than the 

 separation due to a difference of a unit in atomic weight. There is 

 no trace of doubling, and it seems clear that if lithium consists of 

 a mixture of isotopes with atomic weights differing by whole 

 numbers, only that corresponding to an atomic weight of 7 occurs 

 in any considerable quantity. Further experiments are in progress 

 with the object of improving the definition and detecting small 

 proportions of isotopes if these exist. 



