Heinze — Varying degrees of Actinism of theX-Bays. 313 



Aet. XX VI. — Varying degrees of Actinism of the X-Rays ; 

 by John O. Heinze, Jr. 



One is often disappointed, in taking X-ray photographs, at 

 not obtaining good impressions even when the fluoroscope 

 shows a brilliant effect. It, therefore, seems probabie that the 

 rays which are most active in producing fluorescence are not 

 necessarily those which 

 act most vigorously on 

 the photographic plate. 



In order to test this 

 hypothesis I took a num- 

 ber of observations in the 

 following manner : Hav- 

 ing at my command a 

 powerful coil the dis- 

 charges of which could 

 be regulated with great 

 exactness, and also hav- 

 ing a large selection of 

 the most approved X-ray 

 tubes which had been ex- 

 hausted under my per- 

 sonal superintendence and 

 the behavior of which had 

 been carefully studied, I 

 made a number of expo- 

 sures and noted at the 

 same time the appear- 

 ance of the object in the 

 fluoroscope. Fig. 1 shows 

 the results obtained. 



The exposures were 

 made through a slot in a 

 thick lead plate placed 

 between the tube and the 

 negative. The latter was 

 moved along one stop for 



each minute of exposure; and the intensity of the secondary 

 current was varied with each exposure, starting at one minute 

 with the weakest current and ending at the eighth minute 

 with the strongest current. It will be seen that at the fifth 

 minute the greatest actinic effect was obtained and at eight 

 the most brilliant screen and poorest actinic light. The coil 

 which was used in this experiment is one constructed by me 



