Gases by penetrating Réntgen and Radium Rays. 617 
On the other hand, J. J. Thomson, using a thicker lead 
case round the radium employed, failed to obtain any such 
results (Soddy, Radioactivity, p. 181). McClelland’s obser- 
vations by other methods also indicate that the y rays do not 
carry a charge (Phil. Mag. July 1904). 
Paschen, in his second paper, adds further indirect evidence 
of the view that the rays are projected particles with a nega- 
tive charge. 
Since this paper was forwarded to England, the writer has 
made some further experiments, which form the subject 
matter of a future communication. 
It may be convenient to give a brief summary :— 
(1) An endeavour to deflect the y rays in a very powerful 
magnetic field has failed to show any curvature of the rays. 
(2) The @ rays can be deflected entirely away from the 
y rays, so that the two classes of rays belong to different 
types. 
"G) If radium is enclosed in a mass of lead, several centi- 
metres thick, negatively charged particles are projected from 
the outer layers of the lead ; these can be readily deviated in 
a magnetic field and are absorbed by one or two millimetres of 
lead, whereas the y rays will penetrate several centimetres. 
Thus the y rays vive rise to secondary radiation of the cathode 
type, and it is these rays which Paschen has detected and 
which he incorrectly concluded to be ¥ rays. 
Direct experiments by Becquerel, Rut! hertord, and Villard 
have failed to detect any deflexion of the y rays in a powerful 
magnetic field. } 
The theoretical aspect of the case is summarized by 
Rutherford in ‘ Nature,’ 10th March, 1904 :— 
“As a result of the sudden expulsion of the # particle 
from radium, it is to be expected that a narrow electro- 
magnetic pulse, 7. e. a ‘ hard’ or penetrating type of Rontgen 
rays would be generated. In addition, on account of the 
great speed of the 8 particle, it is able to penetrate through 
a considerable thickness of matter before it is stopped. A 
broad pulse or ‘soft’ Réntgen ray should thus arise at the 
point of incidence of the 6 rays.’ 
It has been pointed out that the y rays arise at the time of 
the expulsion of the 8 ray and not by the bombardment of 
the radium itself, since the amount of y rays from radium is 
independent of its degree of concentration. 
From the present theoretical view that Réntgen rays are 
pulses, it follows that a type of Réntgen rays should be 
produced by the @ ray, and from other evidence we should 
expect these to be of a very penetrating character, 
