tiki 
THE 
LONDON, EDINBURGH, and DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[SIXTH SERIES.] 
JAKUAR Y 1908. 
I. The Relation of Mass to Energy. By Daniel F. Comstock, 
Ph.D., Instructor in Theoretical Physics, Mass. Institute 
of Technology, Boston*. 
1. "VX/TEETHEE the inertia of matter has or has not a 
▼ T complete electromagnetic explanation is a question 
that it will perhaps take many years to answer with any 
degree o£ certainty. The experiments of Kaufmann seem to 
prove that in the case of a single electron the mass is entirely 
of this origin : and it is impossible therefore to avoid the con- 
clusion that at least a fraction of ordinary material inertia is 
also electromagnetic. Doubtless there is a psychological 
cause for our reluctance to accept the electromagnetic expla- 
nation as complete, constant familiarity with ponderable 
bodies having blinded us to the possibility of anything being- 
more fundamental ; but certain it is, that if we free ourselves 
from prejudice as much as possible and adopt the well-tried 
policy of choosing the simplest theory which adequatelv 
represents the phenomena, — the theory that is, which involves 
the least number of variables, — we must decide in favour of 
the complete electromagnetic explanation, which involves only 
the pether and its properties. 
2. The complexity of the Zeeman effect and the relations 
* Communicated by the Author. 
Phil. Mag. S. 6. Vol. 15. No. 85. Jan. 1908. B 
