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SCIENCE. 



[N. S. Vol. III. No. 72. 



(f) It may be asked in what way the air 

 loses this property communicated to it by 

 the X-rays. Whether it loses it as time 

 goes on, without coming into contact with 

 other bodies, is still doubtful. It is quite 

 certain, on the other hand, that a short dis- 

 turbance of the air by a body of large sur- 

 face, which need not be electrified, can 

 render the air inoperative. If one pushes, 

 for example, a sufiBciently thick plug of cot- 

 ton wool so far into the tube that the air 

 which has been traversed by the rays must 

 stream through the cotton wool before it 

 reaches the ball, the charge of the ball re- 

 mains unchanged when suction is com- 

 menced. If the plug is placed exactlj- in 

 front of the aluminum window the result is 

 the same as if there were no cotton wool, 

 a proof that dust particles are not the cause 

 of the observed discharge. Wire gauze acts 

 in the same way as cotton wool, but the 

 meshes must be very small and several lay- 

 ers must be placed one over the other if we 

 want the air to be active. If the nets are 

 not connected to earth, as heretofore, but 

 connected to a constant-potential source of 

 electricity, I have always observed what I 

 expected ; however, these investigations are 

 not concluded. 



((/) If the electrified bodies are placed in 

 dry hydrogen instead of air they are equally 

 well discharged. The discharge in hy- 

 drogen seems to me somewhat slower. 

 This observation is not, however, very re- 

 liable, on account of the difiBculty of secur- 

 ing equally powerful X-i-aj's in successive 

 experiments. The method of filling the ap- 

 paratus with hydrogen precluded the possi- 

 bility of the thin layer of air which clings 

 to the surface of the bodies at the com- 

 mencement playing an appreciable part in 

 connection with the discharge. 



(/i) In highly-exhausted vessels the dis- 

 charge of a body in the path of the X-rays 

 takes place far more slowlj' — in one case it 

 was, for instance, 70 times more slowly — 



than in the same vessels when filled with 

 air or hydrogen at atmospheric pressure. 



(i) Experiments on the behavior of a 

 mixture of chlorine and hydrogen, when 

 under the influence of the X-rays, have 

 been commenced. 



(j) Finally, I should like to mention that 

 the results of the investigations on the dis- 

 charging property of the X-rays, in which 

 the influence of the surrounding gases was 

 not taken into account, should be for the 

 most part accepted with reserve. 



§ 19. In many cases it is of advantage to 

 put in circuit between the X-ray producer 

 and the Euhmkorfl' coil a Tesla condenser 

 and transformer. This arrangement has the 

 following advantages : Firstly, the dis- 

 charge apparatus gets less hot, and there is 

 less probability of its being pierced; sec- 

 ondly, the vacuum lasts longer, at least this 

 was the case with my apparatus ; and 

 thirdly, the apparatus produces stronger 

 X-rays. In apparatus which was either not 

 sufficiently or too highly exhausted to allow 

 the Euhmkorff coil alone to work well, the 

 use of a Tesla transformer was of great ad- 

 vantage. 



The question now arises — and I may be 

 permitted to mention it here, though I am 

 at present not in a position to give answer 

 to it — whether it be possible to generate X- 

 rays by means of a continuous discharge at 

 a constant discharge potential, or whether 

 oscillations of the potential are invariably 

 necessary for their production. 



§ 20. In § 13 of my first communication 

 it was stated that X-rays not only originate 

 in glass, but also in aluminum. Continu- 

 ing my reseai'ches in this direction, I have 

 found no solid bodies incapable of genera- 

 ting X-rays under the influence of cathode 

 rays. I know of no reason why liquids 

 and gases should not behave in the same 

 way. 



Quantitative differences in the behavior 

 of diff'erent bodies have, however, revealed 



