302 Cooksey — Corpuscular Hays produced in 



and soft primary rays fewer corpuscles are produced, the less 

 dense the metal. In the case of copper and nickel, which have 

 the same density, the ratios are the same in the case of the soft 

 primary rays ; for the hard primary rays the ratio is much 

 smaller for copper than for nickel, but it will be noticed that 

 the hardness of the primary rays used on copper was consider- 

 ably less than for the rays used on nickel. In the case of tin and 

 zinc, which have nearly the same density, and on which primary 

 rays of nearly the same hardness were used, we find the corre- 

 sponding ratios nearly equal. In the case of silver, which is only 

 slightly less dense than lead, there are much fewer corpuscles 

 produced than in the lead by the soft primary rays, but the 

 hard primary rays seem to produce more in the silver than in 

 the lead. 



It will be noticed in the case of nickel, zinc, and copper for 

 the hard primary rays, and in silver for both soft and hard rays, 

 that N/N z is larger than N'/N/. This means that of the 

 total number of corpuscles produced a less proportion escapes 

 from these metals than from lead, which would not be 

 expected since the corpuscles should be more absorbed in lead, 

 owing to its greater density, than in the other metals. But 



reference to the values of — -, the ratio of the absorption of the 



A 



primary rays in lead, to that in the other metals, will show that 

 the hard, and in the case of silver also the soft, primary rays 

 are absorbed to a much greater extent in the lead than in the 

 above mentioned metals ; while the corpuscular rays coming 

 from lead for hard primary rays possess nearly the same pene- 

 trating power as those from zinc and copper, and greater 

 penetrating power than those from silver and nickel, as can 

 be seen from the values of k/A' t . Therefore for equal absorp- 

 tions of the primary rays the corpuscles must be produced 

 much nearer to the surface in lead than in the other metals, 

 and consequently a greater proportion of the number produced 

 will escape from the lead than from the other metals, notwith- 

 standing the fact that the corpuscles are more easily absorbed 

 in lead owing to its greater density. 



In the case of the soft primary rays, except for silver and 

 nickel, the value of N/N z is less than the value of N'/N/. 

 But the soft primary rays are absorbed nearly as much by the 

 other metals as by lead, and therefore the corpuscles will come 

 from as near the surface in one as in the other, and, the den- 

 sity of lead being the greatest, more will get out of the other 

 metals in proportion to the number produced than out of lead. 

 In the case of silver we see that the absorption of the primary 

 rays in lead is again much the greater. Nickel is the only 

 other exception to the above, while zinc, which is more trans- 



