310 
IOWA ACADEMY OF SCIENCE 
these masses. Keeent developments, especially regarding the 
metal selenium, (Dr. P. C. Brown, Physical Eeview, May, 1915, 
p. 395) lead to the view that the “free” electrons are only tem- 
porarily and probably only to a limited degree free. It appears 
that under different conditions of pressure and intensity of 
illumination, the electrons taking part in electrical conduction 
have different degrees of freedom from the parent atomic struc- 
ture. The present experiment was suggested in the light of 
Dr. Brown’s results. (Loc. cit.) Its outcome appears to sup- 
port the particular view to which he has been led, of the action 
of conducting electrons in metals. 
The Physical Laboratory, 
State University op Iowa. 
