ADAMS. — TRANSMISSION OF RONTGEN RAYS. 



691 



in a two-piece screen of silver and copper does not affect the trans- 

 mission appreciably. This conclusion evidently holds for a considerable 

 range of quality of the incident radiation, as the parallel variations of 

 values in the two columns of ratios in Table X indicate. 



TABLE X. 

 Effect op reversixg the Order of the Metals ix a Two-piece Screen. 



Similar conclusions were deduced from experiments on other pairs of 

 metals. The four metals, copper, silver, aluminium, and tin, were taken 

 two by two in each of the six possible ways, and in every case it was 

 found that the ratio of transmission for the two-piece screen was in- 

 dependent of the order of the pieces, within the experimental error. 



