Rays of Positive Electricity. 241 



it had an electric atomic weight of about the right magni- 

 tude ; it was too faint to admit of accurate measurement. 

 It was, however, stronger on the negative side. The oxygen 

 line was exceptionally strong in this gas. 



One very remarkable fact which appears from the study 

 of these rays is the ease with which the atom of hydrogen 

 acquires a negative charge; this does not harmonize well 

 with the usual view as to the electro-positive character of 

 hydrogen. With this exception the negative charge, as far as 

 my observations have gone, is assumed by, and only assumed 

 by, those ions which have distinctly electro-negative chemical 

 properties, thus leaving out H. The gases which appear on 

 the negative side are 0, 01, ON, all well recognised electro- 

 negative ions. It would thus seem that here we have direct 

 experimental evidence that the atoms of the electro-negative 

 elements can acquire a negative charge when under the 

 same circumstances the atoms of the other elements do not 

 do so. 



Long and Short Lines. — The length of the parabolas on 

 the photographs varies very much from one curve to another ; 

 the least deflected parts are all on the same vertical line, 

 indicating, as we have seen, that the maximum potential 

 difference through which the particles have fallen is the 

 same for all the different kinds of particles which give rise 

 to these lines ; this potential difference is probably the poten- 

 tial difference between the cathode and the negative glow. 

 Though the minimum horizontal deflexion is the same for 

 all the curves, the maximum is very different even when the 

 pressure of the gas in the tube is exceedingly low. As will 

 be seen from the reproduction of the photographs, some of 

 the curves are exceedingly short, so that the horizontal 

 deflexion of any one of the particles producing it is not 

 much greater than the minimum, showing that all these 

 particles have practically fallen through the maximum 

 potential difference, and have therefore probably been pro- 

 duced near the confines of the negative glow. On the other 

 hand, there are on the same photograph some curves of great- 

 length where the maximum horizontal deflexion is at least 

 five or six times the minimum ; the particles which have 

 suffered the maximum deflexion have therefore fallen through 

 a potential difference of less than one-fifth of that between 

 the cathode and the negative glow. Since the electric force 

 increases rapidly near the cathode there will be, at a distance 

 from the cathode much less than one-fifth the thickness of 

 the dark space, a difference of potential amounting to one- 

 fifth that through the whole of the dark space ; hence we 



Phil. Mag. S. 6. Vol. 21. No. 122. Feb. 1911. 11 



