1896.] 



299 



[Leonard. 



of Clinical Medicine seem to prove that another physical characteristic 

 of the x-ray is now known. 



In heating a double-cathode x-ray tube of the focus type, while it 

 was energized by an alternating current, the following phenomenon was 

 noted. 



When the alcohol lamp was held at a point midway between the ca- 

 thodes and at a distance varying from one-half to three inches from the 

 reflectors, the x-ray, as shown in the fluoroscope, and the fluorescence 

 within the tube were seemingly extinguished. 



This was true in tube A, and in no other tube of the double cathode 

 focus type. 



What was the form of interference which the lamp exerted, and why 

 did it apply to one tube and not to all of that type ? 



These queries led to the following experiments in which I was assisted 

 bv Mr. Alfred Watch. 



Diagram of X-Ray Tubes. Cathode Rays • 



X-Rays 



Basing our experiments upon the theory, that it was the aqueous 

 vapor, produced by the combustion of the alcohol, which caused this 

 phenomenon, we substituted for the alcohol lamp a small piece of filter 

 paper saturated with water, and obtained the same result. There was 

 no ettect upon the other tubes, the discharge of x-rays and the 

 fluorescence remaining unaltered. On approaching the wet paper to 

 the cathode a streaming of electricity was observed from the paper or 

 lamp vapor towards the cathode through the wall of the tube and was 

 observed to diminish in quantity as the paper was carried towards the 

 point midway between the cathodes and opposite the reflector, and when 

 it reached this point the x-ray and fluorescence ceased. At all points 

 outside the tube a grounded wire drew a spark from the burner of the 

 lamp, or from the moistened paper. This experiment seems to show 

 that there can be established outside of the x-ray tube a connection 

 between one cathode and the other capable of modifjdug the effect of 

 the electrical discharge within the tube. 



This was proved by using a piece of wet paper so shaped that it ex- 



PROC. AMER. rillLOS. SOC. XXXV. 153. 2li. PRINTED APRIL 20, 1897. 



