May 15, 1896.] 



SCIENCE. 



727 



vicinity of the discharge appai-atus. To 

 this end I made a box of soldered sheet 

 zinc large enough to receive me and the 

 necessary apparatus, and which, even to 

 an opening which could be closed by a zinc 

 door, was quite air-tight. The wall oppo- 

 site the door was almost covered with lead. 

 Near one of the discharge apparatus placed 

 outside, the lead-covered zinc wall was 

 provided with a slot 4 cm. wide, and the 

 opening was then hermetically closed with 

 a thin aluminum sheet. Through this 

 window the X-rays could come into the 

 observation box. I have observed the fol- 

 lowing phenomena : 



(a) Positively or negatively electrified 

 bodies in air are discharged when placed 

 in the path of X-rays, and the more quickly 

 the more powerful the rays. The intensity 

 of the rays was estimated by their effect 

 on a fluorescent screen or on a photographic 

 plate. It is the same whether the elec- 

 trified bodies are conductors or insulators. 

 Up to the present I have discovered no 

 specific difference in the behavior of differ- 

 ent bodies with regard to the rate of dis- 

 charge, and the same remark applies to the 

 behavior of positive and negative electricity. 

 Nevertheless, it is not impossible that small 

 differences exist. 



(6) If an electrical conductor is sur- 

 roiinded by a solid insulator, such as par- 

 affin, instead of by air, the radiation acts as 

 if the insulating envelope were swept by a 

 flame connected to earth. 



■ (e) If this insulating envelope is closely 

 surrounded by a conductor connected to 

 earth, which should like the insulator be 

 transparent to X-rays, the radiation, with 

 the means at my disposal, apparently no 

 longer acts on the inner electrified conductor. 



(d) The observations described in a, h 

 and c tend to show that air traversed by 

 X-rays possesses the property of discharg- 

 ing electrified bodies with which it comes 

 in contact. 



(e) If this be really the case, and if,further, 

 the air retains this property for some time 

 after the X-rays have been extinguished, 

 it must be possible to discharge electrified 

 bodies by such air, although the bodies 

 themselves are not in the path of the rays. 



It is possible to convince oneself in vari- 

 ous ways that this actually happens. I will 

 describe one arrangement, perhaps not the 

 simplest possible. I employed a brass tube 

 3 cm. in diameter and 45 cm. long. A few 

 centimeters from one end a portion of the 

 tube was cut away and replaced by a thin 

 sheet of aluminum. At the other end an 

 insulated brass ball fastened to a metal rod 

 was led into the tube through an air-tight 

 gland. Between the ball and the closed 

 end of the tube a side tube was soldered on, 

 which could be placed in communication 

 with an aspirator. When the aspirator 

 was worked the brass ball was surrounded 

 by air, which on its way through the tube 

 went past the aluminum window. The 

 distance from the window to the ball was 

 over 20 cm. I arranged the tube in the 

 zinc box in such a manner that the X-rays 

 passed through the aluminum window at 

 right angles to the axis of the tube, so that 

 the insulated ball was beyond the reach of 

 the rays in the shadow. The tube and the 

 zinc box were connected together ; the ball 

 was connected to a Hankel electroscope. It 

 was seen that a charge (positive or nega- 

 tive) communicated to the ball was not 

 affected by the X-rays so long as the air in 

 the tube was at rest, but that the charge 

 immediately diminished considerably when 

 the aspirator caused the air traversed by 

 the rays to stream past the ball. If the 

 ball by being connected to accumulators 

 was kept at a constant potential, and if air 

 which had been traversed by the rays was 

 sucked through the tube, an electric cur- 

 rent was started as if the ball had been 

 connected with the wall of the tube by a 

 bad conductor. 



