132 Trowbridge and Burbank — Source of the X-rays. 



different angles, produced elongated shadows. In the next 

 form of tube, the wire passing through the tube was no longer 

 straight, but was bent in the manner represented in fig. 8. In 

 this form of tube there was a brilliant caustic formed on the 

 sides of the tube opposite the concave side of the wire, and 

 this brilliant caustic threw distorted shadows of the bent wire 

 on the opposite side of the tube. It was evident that the 

 X-rays were given off at right angles to the surface of this 

 wire, and therefore coincided in direction with the lines of 

 electrostatic force. We next experimented with the form of 

 tube represented in fig. 9. This consisted of a large thin bulb 

 five inches in diameter, enclosing a continuous conductor, the 

 center of which consisted of an aluminum mirror. When 

 this tube was exhausted to a very high degree, the mirror 

 formed a bright fluorescent spot on the bulb, the position of 

 which could be readily changed by means of a magnet. When 

 the exhaustion was carried to a very high degree, reversing 

 the current from a Ruhmkorf coil through the tube caused no 

 marked difference in the appearances in the tube : at a lower 

 degree, however, a marked difference resulted. With the em- 

 ployment of a powerful Ruhmkorf coil giving sparks of at 

 least eight inches, X-rays could be detected in this tube, and 

 when the tube was connected to the Plante machine, the X-rays 

 gave strong effects in the fluoroscope. 



In order to test the question whether the so-called cathode 

 rays and X-rays are generated primarily only at the cathode, 

 a very large resistance of distilled water was interposed in the 

 circuit with the continuous wire tube (fig. 9) in order to damp 

 any oscillations which might arise. The circuit thus consisted 

 of the tube, the water resistance, a spark gap and the secondary 

 coil of a large Ruhmkorf. The tube was connected at first 

 permanently to the air pump. As the exhaustion proceeded a 

 beam of rays proceeded from the mirror on the continuous 

 conductor which was focused on the wall of the tube. This 

 beam was more brilliant and produced a stronger fluorescence 

 on the tube when the wire was negative than when it was posi- 

 tive. At a higher stage of the vacuum, however, very little 

 if any difference could be detected in the appearance of the 

 tube, and X-rays could be detected outside the tube opposite 

 the fluorescent spot caused by the mirror. That is, the X-rays 

 were given off both when the wire constituted the cathode of 

 the circuit and also the anode. It seems therefore that the 

 term cathode rays is not a general one. It would seem that 

 electric rays might be a more comprehensive one for both 

 cathode rays and X-rays. 



Furthermore the phenomenon of electrostatic induction 

 plays an important part in the phenomena of the so-called 



