84 ROYAL SOCIETY OF CANADA 
In a similar way he showed that the same ratio was obtained for 
negative particles shot off from the glowing carbon filament of an 
incandescent lamp. 
We thus see that “electrons” produced under widely different 
conditions are all of the same size and of mass about 1-1000 of the 
hydrogen atom. 
We have so far considered electrons which have been produced 
by the agency of light, heat, and the electric discharge, but there is 
also very strong evidence that these electrons are always present in 
matter and may manifest their presence under special conditions. 
Zeeman discovered in 1896 that the bright lines in the spectra 
of many substances were displaced by a strong magnetic field acting 
on the source of light. 
Later experiments showed that under certain conditions one of 
the D-lines of sodium, for example, was transformed into a triplet by 
the action of a magnetic field. These lines showed definite peculiar- 
ities in regard to the polarization of the light. These results were 
in direct confirmation of a theory advanced by Lorentz which. con- 
sidered light to be due to the rotation or oscillations of the electrons 
in the molecule. The equations representing the change of period 
of the light in a magnetic field involved the ratio =. From the 
wt 
change in wave length of the light vibration it was possible to deduce 
the value of this ratio. The value of was again found to be 
about 107, showing that in all probability that light was due to the 
rotation or oscillation of electrons in a molecule, and that the mass 
of the electron was much smaller than the atom itself. 
Not only are these electrons present in matter, but in some 
cases they are spontaneously emitted from it. Becquerel has shown 
that the radioactive substances uranium and radium give out some 
rays deviable in a magnetic field. The writer has recently found 
that thorium, the other permanent radioactive substance, also pos- 
sesses the same property. These rays were found to be analogous 
in all respects to high velocity cathode rays. They were deviated 
by a magnetic and by an electric field and carried with them a nega- 
tive charge. Becquerel also showed that the particles travelled with a 
velocity not very different from the velocity of light, while the ratio 
of —— was again about 107. 
Wt 
Many of the electrons shot off from radioactive substances have 
a much higher velocity than the cathode rays in a vacuum tube. The 
highest velocity observed for the latter is about one-third of the 
