58 

 NOTES ON RONTGEN KAYS 



BY H. A. ROWLAND, N. R. CARMICHAEL, AND L. J. BRIGGS 

 [Electrical World, XXVII, 452, 1896] 



In the ' American Journal of Science ' for March we made a few notes 

 of our researches on the Rb'ntgen rays, reaching the provisional con- 

 clusion that the main source of the rays was at the anode, and that the 

 cathode rays seemed to have nothing to do with the phenomena pre- 

 sented. A further study of the source of the rays in many other tubes 

 has led us to modify this conclusion somewhat, for, while we still think 

 the anode or its equivalent is the main source of the rays, yet we now 

 have evidence in some of the tubes that it is necessary for the cathode 

 rays to fall on the anode in order that the Rontgen rays may be formed. 



In our tubes with a very high vacuum the other sources of rays are 

 very faint indeed. We have never obtained any rays from the cathode 

 except in one case, where undoubtedly there were electrical oscillations 

 which made the cathode momentarily an anode. It can be readily proved 

 that these oscillations always exist in the case of low resistance tubes, 

 and these are probably the cause of many errors in estimating the 

 source of the rays. 



In some cases we have found very faint sources of rays as Rontgen 

 found them, where the cathode rays struck the glass, but not where they 

 struck a piece of platinum kept at nearly zero potential. On the anode 

 theory, this might be explained by the fact that the bombarding cathode 

 rays, coming in periodical electrified showers, alternately raise and 

 lower the potential of the glass, thus making it alternately an anode and 

 cathode. In the case of the platinum, this could not occur to the same 

 extent. 



That feeble Rontgen rays emanate from some bodies when bombarded 

 by the cathode rays, we are willing to admit, and, in fact, had long ago 

 come to that conclusion. But we do not agree with Prof. Elihu Thom- 

 son's general conclusion that these rays are always given out from bom- 

 barded surfaces, as we have a tube, with platinum in the focus of a con- 

 cave electrode, which emits no rays whatever from the platinum, even 



