Irregularities in Radiation from Radioactive Bodies. 539 
the annexed curves ; for further details my paper may be 
referred to. From this fact I will not draw any further 
20'r 
10' 
to'- 
SO' - 
*0' 
30'- 
20' 
515 520 525 
I = Double magnetic rotation of the plane of polarization in a solution 
of chloride of erbium, | to i normal, in glass vessel. Field 
7500 gauss 
11= The same for water, in the same vessel. 
conclusions in this short notice. Of course the peculiar be- 
haviour of the rotation will be closely connected with the very 
complicated structure of the band, not to be seen in the liquid 
solution, but very clearly in solid solutions, especially at 
liquid air temperature *. 
I am busy continuing these investigations, as well as 
those on absorption, refraction, and related phenomena, with 
different salts of the rare earths, solid and dissolved, and am 
using for the purpose a monochromatic autocollimating 
illuminator, made by Zeiss in Jena, a description of which 
will shortly appear. 
Berlin, Bosscha Laboratory, 
Feb. 15, 1908. 
L. The Irregularities in the Radiation from Radioactive 
Bodies. By Hans Geiger, Ph.D., John Harling Fellow, 
University of Manchester -j*. 
IX all experiments in which the ionization currents due to 
two radioactive substances are balanced against each 
other by means of an electrometer, it is not found possible to 
obtain an exact balance. The needle of the electrometer 
always moves quite irregularly over a certain number of 
divisions on the scale. This effect cannot be eliminated, no 
matter how much care is taken in the adjustment. Bronson J, 
who was troubled by this effect in the use of his steady 
* H. du Bcis & G. J. Elias, loc. cit. 
t Communicated by Professor E. Rutherford, F.R.S. 
X Bronson, Phil. Mag. Jan. 1906, p. 143. 
