24:8 Sir J. J. Thomson : FurtJi 



ter 



ov r er other negative atoms as positive hydrogen has over other 

 positive atoms. Thus on all the plates the line corresponding 

 to the negative hydrogen atom is well marked, often com- 

 parable with the line due to the negative oxygen atom. With 

 the Faraday cylinder method, the negative hydrogen atoms 

 can only just be detected, while the negative oxygen ones 

 produce large deflexions. 



The discrepancy between the effects produced by hydrogen 

 atoms and an equal number of heavy atoms is even more 

 marked with a willemite screen than with a photographic 

 plate : thus the willemite screen may show the hydrogen 

 lines intensely bright, while the CO line is hardly visible,, 

 when measurements made with the Faraday cylinder show 

 that the number of hydrogen particles is only a few per cent, 

 of the number of CO particles. An interesting point and 

 one that requires further investigation, is that with the 

 heaviest particles of all, the mercury ones, the discrepancy 

 between the results obtained with the Faraday cylinder and 

 the photographic plate is not so great as it is with some of 

 the lighter particles. 



When the positive rays are detected by a phosphorescent 

 screen or a photographic plate, we find that whatever gas 

 may be in the discharge-tube, the hydrogen lines are strong;, 

 this suggests that in all gases there are a great number 

 of positive carriers having the same mass as the atom of 

 hydrogen. With the Faraday cylinder method, however, 

 we find that the number of charged atoms of hydrogen is 

 small unless hydrogen is introduced into the tube ; this small 

 quantity is not greater than that which might be accounted 

 for by gas given out by the electrodes or liberated from the 

 walls of the discharge-tube. The results obtained with the 

 screen and plate are thus due to the abnormal sensitiveness 

 of these agents to the rapidly moving hydrogen atoms, which 

 makes them give a false estimate of the number of these atoms 

 taking part in the discharge. 



Are the atoms in the molecule of a gas charged one ivith 

 positive the other with negative electricity ?. — It is a matter 

 of fundamental importance to know if the atoms in the- 

 molecules of gases, compound or elementary, are charged 

 with electricity or not. In a molecule of hydrogen, for 

 example, is one atom positively, the other negatively, 

 charged ? In a molecule of hydrochloric acid gas, is the 

 hydrogen positively, the chlorine negatively, charged ? In 

 a molecule of ammonia, has the nitrogen atom three 

 negative charges and each of the hydrogen atoms one 



