Trowbridge and Burbank — Source of the X-rays. 129 



Art. XIX. — The Source of the X-rays ; by John Trow- 

 bridge and John E. Burbank. 



The experiments described in this paper were conducted 

 with Crookes tubes containing no interval between the anode 

 and the cathode: and no discharge therefore in the usual sense 

 occurred in the tubes. A continuous conductor was led through 

 the rarified tube, and it was discovered that the X-rays were 

 given off from every element of this conductor at right angles 

 to its surface when a disruptive discharge occurred in the cir- 

 cuit of which the tube formed a part. This remarkable result 

 was obtained by means of the very high electromotive force 

 obtained by a Plante rheostatic machine which was charged by 

 ten thousand storage cells. We shall describe our experiments 

 with the various tubes we employed and in conclusion state 

 our results. 



The first tube is shown in fig. 1 (p. 131). It consisted of a 

 straight wire tube joined to an ordinary Crookes tube of the focus 

 pattern. This latter tube was joined to the straight wire tube 

 in order to test the vacuum in the latter and to be sure that the 

 necessary conditions existed for the production of the X-rays. 

 When the terminals of the straight wire tube were connected 

 to the Plante machine, and the latter was excited, the entire 

 tube fluoresced brilliantly. This fluorescence was especially 

 bright in the connecting tube between the straight wire tube 

 and the Crookes tube, and a beam of light passed across the 

 Crookes tube and formed a fluorescent spot on its bulb. 



Photographic plates were exposed opposite to the thin bulb 

 on the straight wire tube. These plates were carefully insu- 

 lated from the ground and were covered in one case with a 

 sheet of hard rubber -J- of an inch in thickness, and in another 

 case by a sheet of glass about J inch in thickness. A power- 

 ful brush discharge was seen in the dark room to pass from the 

 thin bulb of the tube to the insulator which covered the plates, 

 and on developing the plates they were found to be covered 

 with star-like clusters surrounded by nebulous patches. It was 

 evident that the brush discharge had produced discharges at 

 the surface of the dry plate, even through plates of glass -| an 

 inch in thickness. Moreover there was a general darkening 

 of the surface of the plate which indicated the action of the 

 X-rays. ~No metallic objects could be placed upon the dry 

 plates, for a powerful spark immediately passed to them and 

 punctured the tubes. The darkening, however, was apparently 

 diminished under strips of glass., although the effect of the 

 brush discharge masked the effect of the X-rays. 



Am. Jour. Sci.— Fourth Series, Yol. Y, No. 26.— February, 1898. 

 9 



