





Secondary Réntgen Radiation. DDL 
TaBLeE II. 
‘Primary Radiation) Duration of pEainicy Electro- Secondary Blectro 
| in Experiment. | Experiment. _ Scope Deflexion. | scope Deflexion. 
| | 
| Rays direct from minutes. ) 
| BR ie sccnc cused. | 1:3 | 164°6 8-9 | 
Secondary ays / 
|=! from copper ... 50 | 34-4 3°8 | 
| _ 60 | 2-4 18 | 
| Rays direct from / 
Peal... 5s | NN hati 75 
| Secondary rays / 
| from copper .... 60 ) 71 55 
None: screened 
| by lead plate... 40 | 1-4 1-4 | 


After correction for the normal ionization, and for absorp- 
tion of the secondary rays from copper in their passage from 
aperture R to electroscope N of the order of 10 per cent., 
these readings were :-— 
Ratio of Primary to Secondary 
Electroscope Deflexion. 
Rays direct from bulb . . . . . 100 to 5°4 
Secondary rays from copper . . . 100 to 64 
Primary Radiation. 
Rays direct from bulb. . . . . 100to4 
Secondary rays from copper . . . 100 to 4:4 
As the boundaries of the beam proceeding from copper 
were necessarily not so well defined as those of the beam 
direct from the bulb, on account of the much greater area of 
the source ot radiation, the two were not accurately com- 
pared, so that the agreement between these results is quite as 
close as could have been expected. (Quantitative results were 
thus obtained, showing that the secondary radiation from 
copper is of the same nature as the primary radiation, for 
the secondary radiation is productive of a tertiary radiation 
whose intensity bears the same relation to the intensity of the 
secondary as that of a secondary from air bears to the intensity 
of the primary producing it. 
It has been shown that the intensely penetrating rays trans- 
mitted through sheets of aluminium give a slightly higher 
ratio of secondary ionization to primary ionization than the 
moreabsorbable radiation; and that this resultisdue principally, 
if not entirely, to the greater difference in ionizing power 
