1913] on the Method of Positive Rays 598 



in the tube. I now turn to the pliotograph of the h'ghter constituents 

 shown in Fig. ;] ; here we find the lines of hehuni, of neon (very 

 strong), of argon, and in addition there is a line corresponding to an 

 atomic weight 22, which cannot be identified with the line due to 

 any known gas. 1 thought at first that this line, since its atomic 

 weight is one-half that of ,-000, must be due to a carbonic acid 

 molecule with a double charge of electricity, and on some of the 

 plates a faint line at 44 could be detected. On passing the gas 

 slowly through tubes immersed in liquid air the line at 44 com- 

 pletely disappeared, while the brightness of the one at 22 was not 

 affected. 



The origin of this line presents many points of interest ; there 

 are no known gaseous compounds of any of the recognized elements 

 which have this molecular weight. Again, if we accept Mendeleef's 

 Periodic Law, there is no room for a new element with this atomic 

 weight. The fact that this line is bright in the sample when the 

 neon line is extraordinarily bright, and invisible in the other when 

 the neon is comparatively feeble, suggests that it may possibly be a 

 compound of neon and hydrogen, NeHa, though no direct evidence 

 of the combination of these inert gases has hitherto been found. I 

 have two photographs of the discharge through helium in which 

 there is a strong line, 6, which could be explained by the compound 

 HeHo, but, as I have never again been able to get these lines, I do 

 not wish to lay much stress on this point. There is, however, the 

 possibility that we may be interpreting Mendeleef's law too rigidly, 

 and that in the neighbourhood of the atomic weight of neon there 

 may be a group of two or more elements with similar properties, just 

 as in another part of the table we have the group iron, nickel, and 

 cobalt. From the relative intensities of the 22 line and the neon 

 line we may conclude that the quantity of the gas giving the 22 Hue 

 is only a small fraction of the quantity of neon. 



Let me direct your attention again to the photograph of the 

 heavier gases in the atmosphere. You will notice that the parabolas 

 corresponding to many of the elements start from points which are 

 all in the same vertical line ; this indicates that the atoms or molecules 

 which form these parabolas all carry the same charge. Several of 

 these lines, however, do not follow this rule ; you will notice, for 

 example, that the neon line has a prolongation which comes nearer 

 than the normal line to the vertical line drawn through the unde- 

 flected spot. Measurement of the photograph shows that the neon line 

 Ijegins at a distance from this vertical line which is only half the 

 normal distance ; this shows that some of the neon atoms in the 

 positive rings possess two charges of electricity ; the majority of them, 

 however, only possess one. If you examine the argon line you will 

 find that it comes even nearer to the vertical than the neon line : in 

 fact, it begins at a distance from the vertical only one-third of the 



2 R 2 



