different Metals by Rontgen Hays. 



301 



passing through the origin and the first point was multiplied 

 by the percentage of rays absorbed by the first layer of alumin- 

 ium, and the slope of the line passing through the first and 

 remaining points was multiplied by the percentage of rays 

 remaining unabsorbed by the first layer, and the sum of the 

 two numbers thus found divided by 100. This seems to me 

 to give the fairest value of k when the rays are. not homoge- 

 neous. 



Table IX. 



Metal Hard k P - * * ^ Q N^ N 



pi 1 hi kf Qt NY N; 



L( ;? d nni o"? i' 00 1-00 1-0 ° 1-00 I' 00 i' 00 i' 00 



0'92 6' i 



Silver 0'52 4-6 2'0 078 0-61 0-52 041 0"59 



" 0-90 3-8 2-0 1-03 1-10 0"77 0*79 1'60 



Nickel 0-59 5-5 ft . Hq 1'4 0-93 0"87 0'36 0'33 0"35 



" 0-94 4-9 1-5 1-30 1'70 0'35 0'46 0"70 



Tin 0-59 4-2 1-1 0"7l 0'51 0"64 0"55 0'23 



" 0-95 3-6 1-0 0-97 0'94 0'7o 0"73 0'46 



Zinc 0-66 4-5 1«5 076 0'58 0'41 0'31 0'22 



" 0-80 3-7 1-9 1-00 TOO 0-35 0*35 042 



Copper 0-63 5-5 7 1-3 0-93 0'87 0-39 0'36 0'35 



" 0-82 3-7 1-6 1-00 1-00 0-33 0-33 0'42 



Table 9 gives the values of the ratios of the different quanti- 

 ties in the formula. The absolute values of k, given in the 

 second column, are not the true coefficients of absorption, but 

 the absorption per 0*01 mm of aluminium calculated from the 

 common logarithms and not the natural logarithms ; but as k 

 comes into the formula only as a ratio, the' other constants 

 cancel. The numbers after the metals in the first column 

 denote the hardness of the primary rays used on the metal and 

 on lead when the two were compared. The seventh column 

 gives the ratio of intensity of ionization produced by the cor- 

 puscular secondary rays from the different metals to that 

 which was due to the rays from lead, as measured experiment- 

 ally for the different hardnesses given. The numbers in the 

 eighth column are the ratios of the number of corpuscles 

 which get out of the different metals to those which get out 

 of lead. The numbers in the last column of the table repre- 

 sent the ratios of the total number of corpuscles produced in 

 the metals to the number produced in lead for equal absorptions 

 of the primary rays of equal intensity, as calculated from the 

 formula. 



It will be seen at once that, in all cases, this ratio is larger 

 for the harder primary rays, in fact in silver the harder prim- 

 ary rays produce more corpuscles than in lead. For both hard 



An. Jour. Sci. — Fourth Series, Vol. XXIV, No. 142. — October. 1907. 



21 



