62 SCIENCE PROGRESS 



substance H 3+ . A photograph showing this line is reproduced in 

 Plate II; though it is always faint when compared with Hx 

 and H 2 the parabola is nevertheless genuine and has been 

 repeatedly obtained. 



Oxygen. — This gas has probably been experimented with in 

 a more nearly pure state than any other, as it combines with all 

 the impurities given off by the apparatus forming compounds 

 which can be removed by means of liquid air. Plate III was 

 taken with this gas. Hi and H 2 have practically disappeared 

 and nearly the whole of the intensity is in the lines correspond- 

 ing to + 1 6 and + 32, O and 2 respectively. There is a very 

 strong negative line 0_ at — 16. This 0_ line appears on 

 nearly all plates taken when oxygen is present, either free or in 

 combination. No negative corresponding to 2 has been de- 

 tected in highly purified oxygen but the line sometimes appears 

 when other gases are present. The very obvious extension 

 of the + line in Plate III indicates the tendency of the oxygen 

 atom to take up a double charge. 



Nitrogen appears as N ++ , N + and N 2+ ; it never gives a nega- 

 tive parabola. In some of the nitrogen photographs a faint line 

 is found at 42-43 which Prof. Thomson thinks may be due to 

 a compound N 3 or N 3 H. If made from air, nitrogen shows the 

 argon line corresponding to mass 40. 



Carbon appears as C++, C + and C_ when compounds such as 

 the monoxide and dioxide are used. Plate IV, which represents 

 carbon monoxide, shows the negative O and C lines quite 

 clearly and also doubly charged positive ones. On using certain 

 organic compounds, a negative parabola corresponding to a 

 mass 24 is found, which seems to be due to a molecule 

 consisting of two carbon atoms carrying a single negative charge. 



Organic compounds give very complex results but it is beyond 

 the scope of this article to discuss these. The case of methane, 

 CH 4 , however, is comparatively simple and of particular interest. 

 In the case of this gas, if a very narrow canal-ray tube be used, 

 a group of five distinct parabolas is observed differing from each 

 other by mass 1 and corresponding to C, CH, CH 2 , CH 3 and 

 CH 4 respectively, each carrying a single positive charge. 



Chlorine and the other Halogens can be used in the form of 

 their compounds with hydrogen or carbon. They are princi- 

 pally of interest because, like oxygen, they give strong negative 

 atomic parabolas. 



