864 



Dr. A. F. Kovarik on the Absorption and 



Readings were taken by measuring the ionization produced 

 (1) when the rays from c were allowed to pass through a 

 and b, (2) when the rays were reflected by the reflector 

 placed over a, (3) when the rays below c were reflected 

 upwards by placing the reflecting substance under c, (4) when 

 the rays were multiply reflected by placing the reflectors 

 over a and under c. 



When the substance was over a the incident rays were 

 reflected downward in a diffuse manner, and striking the 

 aluminium (-0059 cm.) over the active material become to 

 some extent again reflected, &c. The readings in (2) were 

 therefore always somewhat higher than in (3), which case 

 (except for slight multiple reflexion from the interior of the 

 chamber, amounting to about 3 per cent.) corresponds to the 

 case when reflexion was studied with the hemispherical 

 ionization vessel. Correcting (2) for reflexion and (3) for 

 the absorption and slight multiple reflexion, the two readings 

 always agreed. 



The results of these experiments for the rays from Ea E, 

 using various substances as reflectors, are given in Table VII. 



Table VII. 



Reflecting 

 substance. 



Initial Ionization : Ionization : 



iouiza- reflector reflector 



tion. on top. under. 



Ionization : 



reflector on 



top and below. 



Multiple 



reflexion 



alone. 



Pb 



100 182-0 1726 

 1872 1700 

 1730 170-5 

 1734 1568 

 1575 150-8 

 1600 149-6 

 154-5 141-4 

 150-8 1470 

 143-2 135-7 

 1380 131-5 

 121-5 1210 



122-5 119-0 



3360 

 337-5 

 3130 

 2790 

 2360 

 2330 

 224-2 

 2180 

 1890 

 1717 

 1460 



141-2 



2360 



2375 



2130 



1790 



136 



1330 



124-2 



1180 



890 



71-7 



460 



41-2 



Pt 



Sn 



Ag 



Zn 



Cu 



Ni 



Fe 



S 



Al 



C 



Cardboard... 



The first column gives the substance used for reflecting 

 the /3-particles. In the following four columns are the 

 values of the ionization obtained corresponding to the read- 

 ings taken as given above, the ionization for the incident 

 rays being taken as 100. The last column gives the ionization 

 due to multiple reflexion alone. 



It wall be observed that the substances of higher atomic 

 weight give larger values for the multiple reflexion (Pt for 



