Positive Electrons in the Sodium Atom. 279 
with an exposure o£ one hour. An enlargement was made 
of the plate, which is reproduced in fig. 2'a. Fig. 2 b is a 
contact print from the original negative, and fig. 2 c is a 
print from a plate made with a small two-prism spectroscope, 
showing the entire visible spectrum and the phenomenon at 
the D lines. It will be observed that in the case of some of 
the lines the bright needles of light have withdrawn almost 
entirely from the absorption-spectrum, leaving a dark line. 
(Compare the upper and lower spectra at the points indicated 
by the arrows.) 
If the positive rotation at the D lines can be used as an 
argument that they are due to negatively charged electrons, 
it appears to me that the two types of rotation in the 
channelled spectrum is an evidence that we have both 
positive and negative electrons in the atom. It is perhaps 
unwise to speak of a positive electron, since electron has 
come to mean the disembodied negative charge, after it has 
been expelled from the atom. 
Whether the two types of magnetic rotation proves the 
existence within the atom of both positively and negatively 
charged discrete particles is for the theoretical physicists to 
answer. The observations recorded in this paper merely 
prove that some of the absorption-lines give a rotation 
opposite to that given by the D lines. 
Becquerel has inferred the existence of positive electrons 
in certain crystalline minerals, from the change in the 
appearance of the absorption-band when the crystal is placed 
in a magnetic field. The conditions in this case are, how- 
ever, much more complicated than in the case of sodium 
vapour, for he is dealing with molecules of the rare earths 
in combination with or imbedded in other substances. 
It will be extremely interesting to determine the direction 
of the rotation of the lines in the green and blue region, for 
these have been found to coincide with the regularly spaced 
series of lines in the fluorescence spectra excited by mono- 
chromatic radiations *. I am now investigating this subject 
in collaboration with Mr. Felix Hackett, Fellow of the 
Royal University of Ireland. 
* See previous paper on " The Fluorescence and Magnetic Rotation 
Spectra of Sodium Vapour, and their Analysis." Phil. Mag. Nov. 1906. 
