3i6 



NA TURE 



[August 5, 1897 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of rejected 

 vtanuscripts intended for this or any other part of NATURE. 

 No- notice is taken of anonymous communications.'] 



Rontgen Ray Theory. 



The most important question whether Rontgen rays are to be 

 considered as falling into the domain of light, or whether they 

 are something else, has occupied so many minds, that the liter- 

 ature on this subject has grown enormously ; but is it settled yet 

 whether they are transversal waves of very small wave-length, 

 or longitudinal waves, or vortex motion of the ether, or 

 longitudinal impulses, or due to electromagnetic dispersion, or 

 radiant matter? 



Having read so many theories, with so many supporters and 

 opposers, one gets puzzled what to believe. 



Not a small part of the confusion is caused by the number of 

 contradictory experiments ; and no wonder at this, the question 

 being, in fact, of the utmost complication ; that is to say, not 

 only as to the nature of the rays themselves, but also the way in 

 which to get them. 



Being engaged in the study of silent electric discharges, it 

 was rather in our line to consider the question of kathodic, as 

 well as of our anodic, discharges. Thus we arrived at a 

 conclusion about the nature of Rontgen rays, which explains a 

 great deal, though we. must confess that certain assumptions 

 have to be made. 



This is not an attempt to explain this most difficult problem, 

 but to suggest an hypothesis that is most nearly in accordance 

 with experiments, so far as they go. 



We consider Rontgen rays to be nothing but discharged 

 kathode rays, and will now test this hypothesis by seeing how 

 it will explain some of the most striking experiments and facts. 



As a matter of fact, kathode rays are deflected by a magnet ; 

 they obey the law of attraction of a current by a magnet ; i.e. 

 they behave as a current or stream of negatively charged 

 particles. 



These negative particles impinge upon the glass wall o. the 

 tube, which, as is well known, possesses a strong positive 

 (external) charge. 



Is there anything strange in the idea that those particles may 

 lose their charge when in contact with the positive charged wall, 

 and proceed on their way as discharged particles ? 



These discharged particles cannot, and are not, attracted by a 

 magnet ; why should they be ? Hence the essential difference 

 between kathode and Rontgen rays is explained. 



Rontgen rays would thus discharge a negatively or positively 

 charged body, as a matter of course, since any electrified body, 

 struck by neutral particles, always loses its charge. 



Now let us consider some important details : in the first place, 

 with regard to the focus tube. Some people do not accept the 

 property of being reflected as possessed by the Rontgen rays. 

 It seems to us that the experiments of Tesla with his T-tube, 

 allowing him to take simultaneously a sciagraph from reflected 

 and from rays that have passed through different plates of 

 metal, are conclusive in this respect ; but they prove that the 

 total amount of reflexion varies not very much for the least and 

 for the best reflectors ; the maximum result obtained with zinc 

 (platinum does not seem to have been tested) was only 3 per 

 cent. 



Probably platinum will give a higher percentage of reflected 

 rays ; but even then it does not sufficiently account for the large 

 difference of efficiency of the ordinary and the focus tube. 



According to our theory the real cause of the high efficiency 

 of the focus tube lies in the fact that the kathode rays strike on 

 an actual anode, instead of upon an anode by induction. 



This, so far, is not new. To quote Lodge, in an article written 

 some time ago : " Hence, undoubtedly the X-rays do not start 

 from the kathode, or from anything attached to it, but do start 

 from a surface upon which the kathode rays strike, whether it 

 be an actual anode or only an anti-kathodic surface ; best, 

 however, if it be an actual anode." 



Rontgen and Rowland had discovered the same thing. Ac- 

 cording to our theory, it is evident that the negatively charged 

 particles can lose their charge sooner and more completely when 

 they strike an actual anode, than when they strike an anode by 

 induction (of greater surface, and thus of smaller density). 



NO. 1449. VOL. 56] 



Everybody will agree with Prof. Peckham, where he says 

 that the discharge-tube is a resonator for its coil, and when the 

 coil and tube are properly attuned the maximum effect is 

 obtained. We shoukl say, when the discharging capacity of 

 the surface struck by the kathode rays can keep time with the 

 vibrations of the intermittent current or stream of charged 

 particles, the most intense Rontgen rays will be obtained. 



If discharging— or, better to say, neutralising — of the waves 

 of negative particles from the kathode be not synchronous with 

 their impinging upon the focus or wall, they cannot lose all 

 their charge, and will proceed either as particles with a minute 

 negative charge, or with a minute positive charge, or perhaps 

 mixed with neutral parts. 



The result will be feebler Rontgen rays, and, according to the 

 preponderance of the one or the other particles, these rays will 

 discharge an electrified body, and give it charge according to its 

 own charge. 



Borgmann found that a negatively charged plate, when ex- 

 posed to Rontgen rays, lost its charge to become positively 

 charged ; when the plate was positively charged, it lost part of 

 its charge. 



Righi found just the contrary ; a positively charged plate lost 

 its charge to end with a negative charge. 



Porter, and nearly all other experimenters, found in all cases 

 a complete loss. 



We could explain these differences by admitting that neither 

 Borgmann nor Righi had pure Rontgen rays, but had them 

 mixed with positive and negative rays respectively. 



We consider Porter's Xj X^ X;, rays, and Lenard's gamut of 

 rays of more and less magnetic deflexibility, as Rontgen rays 

 of less and more purity, i.e. neutrality. 



The more perfectly the negative charge has been taken away 

 by the anode— without, however, imparting a positive charge 

 instead — the more intense the Rontgen rays will be, and the 

 stronger penetrating power they will possess. 



It- is hardly necessary to say that it must be very difficult to 

 obtain perfectly neutral rays '; this end will obviously only be 

 attained when the whole system of generating— current, fre- 

 quency, self-induction, capacity, vacuum, size and form of tube, 

 and all the rest — be in true harmony with one another ; and to 

 realise this, means no small thing to do in practice. 



We do not venture to say that our theory explains everything, 

 but we do think it explains much ; we do not ignore the fact 

 that it is difficult to understand how the Crookes' radiant 

 matter could pass through the glass wall as discharged matter, 

 but the theory of ether motion also presents difficulties. Experi- 

 ments on the Lenard rays passing as charged particles through 

 aluminium, are described in Nature of May 27 (p. 93). 



Why should the etheric disturbance in the air answer so 

 closely to the vacuum in the tube ? Why should the rays, if 

 they be ether vibrations, which in any case must be of so short a 

 wave-length that the well-known properties of light do not show, 

 make any difference whether they are obliged to pass through 

 one or the other metal or material? If the intermolecular 

 space be of any influence to them, one should expect refraction 

 in those materials that show greater resistance to the rays 

 passing. 



The strongest proof for our theory is Lafay's experiment, 

 where he found that Rontgen rays, passed through a negatively 

 charged leaf of silver, can again be deflected by a magnet, and 

 in the same direction as the kathode rays in the tube ; and when 

 the leaf was positively charged, in the opposite direction. 



That means that neutral, nondeflectible rays, after re- 

 charging, become again sensitive to the magnet ; the deflection 

 being absolutely in accordance with electromagnetic laws of 

 attraction and repulsion. 



Unfortunately this experiment, repeated by Lodge, has not 

 been confirmed by him ; but it is easy to understand that re- 

 charging, just like discharging, is no simple thing to accom- 

 plish A. VOSMAER. 



F. L. Ortt. 

 Electrical Research Laboratory, The Hague, Holland. 



Some Further Experiments on the X-Rays. 



Messrs. A. Vosmaer and F. L. Ortt, ina paper kindly sent 

 to me by the editor of Nature, have arrived at the conclusion 

 that the X-rays are more or less perfectly discharged particles. 

 Others— Sir W. Crookes, for example— have suggested the 



