THE TRANSMISSION OF llONTGEN RAYS THROUGH 



METALLIC SHEETS. 



Bv John Mkad Adams. 



Presented by John Trowbridge, November 14, 190G. Received January 8, 1907. 



I. Introduction. 



Tins experimental investigation into the phenomena of the trans- 

 mission of Rontgen rays through metallic sheets has grown out of a 

 research which was undertaken three years ago for the purpose of con- 

 firming the measurements of the energy of Rontgen rays then recently 

 made by Dorn,^ Rutherford and McClung,^ Schops,*^ and others. These 

 measurements had been rendered somewhat doubtful by Leininger's * 

 unsuccessful attempt to repeat the work of Rutherford and McClung 

 and of Schops, and it seemed desirable to obtain new evidence on the 

 question by a method diiferent from those already used. 



In general plan the methods of the above-mentioned investigators 

 were similar. Each of them allowed the rays to fall upon thin sheets 

 of metal, and from the heat developed in the metal estimated the 

 energy of the absorbed rays ; then, after making a correction for the 

 fact that not all of the rays incident on the metal are absorbed in it, 

 they were able to calculate the rate at which the tube was radiating 

 energy in the form of Rontgen rays, by assuming from the work of 

 Rontgen ^ and of Guillaume ^ that the emission of energy is nearly 

 uniform in all directions from the target. To reduce the results to 

 absolute measure, it was only necessary to send through the absorbing 

 metal a known electric current of such strength that the heating effect 

 thereby produced was equal to that produced by the absorption of the 

 rays ; the Joulean heat of the current in the metal was then taken to 

 be equal to the energy of the absorbed rays. The methods differed in 



E. Dorn, Ann. d. Phys., 63, 100 (1897). 



E. Uutlierford and K. K. McClunsr, Proc. Roy. Soc, 67, 245 (1900). 



3 Scliups, Zcitsch. fiir Xaturwis.s., 72, 145 (1899). 



4 



F. Leininger, Phys. Zeitsch., 2, m2 (1901). 

 6 W. C. Kontgen, Ann. d. Phys., 64. 22 (1898). 

 6 Ch.-Ed. Guillaume, Comptes Kendus, 123, 450 (189G). 



