VOIy. 6, 1920 
PHYSICS: A. F. KOVARIK 
A STATISTICAL METHOD FOR STUDYING THE RADIATIONS 
FROM RADIOACTIVE SUBSTANCES AND THE X-RAYS 
AND ITS APPLICATION TO SOME y-RAY PROBLEMS 
By Alois F. Kovarik 
S1.0AN Laboratory, YalE University 
Communicated by H. A. Bumstead. Read before the Academy, November 10, 1919 
Statistical methods of studying X-rays and the radiations from radio- 
active substances are important partly because they make it possible, 
to some extent at least, to investigate the individual rays. The scintilla- 
tion method of counting a-particles for example brought decisive evidence 
of the atomic structure of matter. It also made it possible to obtain di- 
rectly the charge on an a-particle. Furthermore, the experiments on the 
scattering of a-particles gave Rutherford some definite know^ledge v^hich 
led to some of the most fruitful suggestions about atomic structure. 
The electrical method of counting a-particles as used by Rutherford and 
Geiger was adapted by Geiger,^ after some changes, to the statistical study 
of both a-particles and j8-particles. Kovarik and McKeehan^ applied 
the method to the investigation of the absorption and scattering of jS- 
particles getting direct information about the /3-particles, whereas the pre- 
vious information was all deduced from ionization experiments which to 
be accurate demands a complete knowledge of the variation of the speed 
and of ionization with speed of a j8-particle passing through matter. By 
this method they also obtained evidence^ supporting the single scattering 
theory of Rutherford and got results in agreement with those deduced 
from Wilson's photographs of the tracks of /3-particles produced by the 
condensation method — another important statistical method. They also 
investigated the magnetic spectra^ of the /3-particles from radium B and 
C and from radium D and E. In their first report they called attention to 
the fact that the 7-ray effects were also counted and that correction had 
to be made for these. 
A more recent development^ in the method makes it possible for each 
ray, upon entering the counting chamber, to cause an audible sound or to 
make an automatic record on paper. The counting chamber generally 
surrounds a specially prepared point. The chamber and the point are 
at a high difference of potential — near the sparking potential. When any 
of the rays enter the counting chamber, ionization is produced and on 
account of the intense field between the point and the chamber, ionization 
by collision results. This magnifies the effect initially produced by the 
ray and this is further magnified by an audion bulb operating a sensitive 
relay which operates a local circuit by means of which a chronograph 
pen makes a record of the fact that an a-particle, a /3-particle, a 7-ray 
pulse or an X-ray pulse has entered the counting chamber. 
Using this method it is possible to investigate some important problems 
