caused by the B and y Rays of Radium. 683 
due to the secondary rays, from the top of the platform, bent 
into the electroscope. 
The rapid fall of the curve shows that the bent rays consist 
of low velocity particles, easily absorbed. When the mag- 
netic field was increased in strength the initia] value was less, 
because some of the rays were curved right on to the platform, 
and absorbed. In this case, too, the curve fell less rapidly, 
so that the rays remaining were more penetrating and had 
higher velocities. The particles are therefore projected with 
various velocities from the lead block. 
Curve III. gives the results when the magnetic field is 
reversed. The added lead screens again produce an increase 
of secondary radiation as in Curve I. After passing the 
maximum, the height of the curve is not materially reduced, 
because the outside rays are bent away from the electroscope 
and cannot be cut down by the lead. 
It may be noted that thin screens placed on the platform 
(fig. 7) increase the secondary radiation, both when there is 
no magnetic field and when the rays are bent into the 
_ electroscope. 
| 
| | 
| Substance. | AEB 8 | No Field. | Rays bent in. 
in mm. / 
A Se -_ ee eee aren, 
cae a | 88 | 176 
7210 eee eee 15 / 93 | 15:0 
LC ee yO | 81 | 13°7 
Wopper, ............ 10 | 9°4 16°7 
Aluminium ...... | 85 10:0 / 176 
Betas! ag dens 2255264 2°0 10-2 | Ly fat 
InpOnItE ...... <2... 50 10°6 20°0 
Basswood ......... 2:0 
The explanation rests in the rise to a maximum shown in 
Curves I. and III. fig. 8, and in fig. 6. The increased values 
are in the inverse order of density. The secondary radiation 
from the lead will pass through a thin substance, and the 
secondary radiation from the added layer caused by the 
y primary rays will reinforce the eftect. 
Discussion of Results. 
Becquerel has shown that the 9 secondary rays can be 
deflected by a magnet. 
_ Curie and Sagnac proved that Rontgen rays striking a 
metal plate cause it tc emit negative electricity and to acquire 
a positive charge; Dorn has proved that such rays can be 
deflected by a magnet. 
