684 Secondary Radiation of B and y Rays of Radium. 
In the present paper it is shown that the electroscope 
method will detect the readily deviable rays caused by the 
y rays, and that such rays are absorbed by a few millimetres 
of lead. 
It is noteworthy that 8, y, and Réntgen rays all give rise 
to a secondary radiation consisting of moving particles having 
a negative charge. 
As cathode rays give rise to Réntgen rays, and the latter 
can cause rays of a cathode type, the process appears rever- 
sible. It is probable therefore that Rontgen, 8, and y rays 
all produce secondary radiations ot the Réntgen type as well 
as those of the 6 type. 
In a recent communication to the .Annalen der Physik 
(Nos. 6, 7, 1904) Paschen has given an account of some 
experiments which he considers to be evidence in favour of 
the view that the y rays consist of negatively charged par- 
ticles moving with higher velocities than the B rays. He 
claims that the y rays are of the type of cathode rays, and 
not of Réntgen rays. 
In the first experiment he enclosed radium in an envelope 
of lead thick enough toabsorb the rays. He found that the 
lead, if well insulated in a vacuum, acquired a positive charge, 
and he justly concluded that negatively charged particles were 
projected from the surface of the lead. He further claimed 
that these negative particles constituted the y rays or a part 
of such rays. 
Now in the experiment described in this paper (figs. 7 
and 8) it has been shown that the particles projected from a 
thick mass of lead, coutainine radium at its centre, are com- 
pletely absorbed by one or two millimetres of lead, and are 
readily deflected in a magnetic field ; whereas the y rays will 
penetrate several centimetres of lead, and have never yet been 
deviated in a more powerful magnetic field. 
It is clear, therefore, that Paschen was not justified in his 
conclusion that the y rays consist of negatively charged par- 
ticles, but that he was really dealing with a secondary radiation 
caused by the y rays, and proceeding frum the outer layers 
of the lead envelope. 
Direct experiments by Becquerel, Rutherford, Villard, and 
others have failed to detect any curvature of the y rays in a 
magnetic field. There is at present no evidence that the 
y rays consist of negatively charged particles. On the other 
hand, the @ rays can be deflected com) letely away from the 
y rays. This abrupt discontinuity in the magnetic spectrum 
indicates that y rays are not merely a group of those @ rays 
which have the highest velocity. 
ij 
Ee 
—— 
