PHYSICS IN 1913 621 



give a line coinciding with this line, but the C0 2 can be removed 

 without influencing the line. J. J. Thomson came to the con- 

 clusion that it corresponded to a new gas of atomic weight 22, 

 closely allied to neon (atomic weight 20), with a single charge. 

 After many attempts Aston, working in the Cavendish labo- 

 ratory, has apparently succeeded in isolating such a gas by 

 allowing the mixed gases (neon and the supposed new gas) 

 to diffuse repeatedly through a porous wall ; owing to the 

 difference in rates of diffusion consequent on the heavier atom 

 of the new gas, a separation would be expected. In this way 

 Aston obtained two gaseous components which showed the 22 

 line in different intensities, and also gave differences of density 

 when weighed on a specially constructed quartz balance. The 

 two gases, however, gave the same spectrum, and in other 

 respects showed like chemical properties, so that on the present 

 evidence it appears they differ in atomic weight, but not in 

 chemical properties ; this is the case with some of the radio- 

 active elements. On Rutherford's nucleus atom theory such a 

 state of things is quite possible, since the chemical and physical 

 properties of an atom depend on the charge on the nucleus, 

 while the atomic weight depends on the inner structure of the 

 nucleus, and may not be proportional to the charge. 



As regards the unknown substance " X 3 " causing the line for 



which — = 3, J. J. Thomson has come to the conclusion that it 



is triatomic hydrogen with one charge. He has shown that 

 it cannot be a carbon atom with four charges, and the fact that it 

 can be obtained by the bombardment by cathode rays from salts 

 containing hydrogen, but not from those which contain no 

 hydrogen, the salts in both cases being previously freed from 

 absorbed gases, lends support to the hydrogen hypothesis. 

 J. J. Thomson has also been examining by the positive ray 

 method the gases given off from a great variety of substances 

 when they are exposed to the bombardment by cathode rays, 

 with special reference to the production of helium, found by 

 Ramsay in old X-ray bulbs, and neon. He finds that in all cases 

 small amounts of helium are liberated, even when the bombarded 

 salts have been dissolved and dried several times to free them 

 from occluded gases. The experiments are still in progress, and 

 the source of the helium must be regarded as still in question. 

 Very recently Strutt has published an account of attempts made 



