190 
PSYCHOLOGY: D. MACKENZIE 
Proc. N. a. S. 
is so short that we cannot use the flicker principle as applied in photometry. 
Accordingly, the loudness balance is found when the flickers of the two 
tones are judged to be equally conspicuous. 
It appears that this balance is definite. Balances can be repeated with 
an error of 5% or less; the tones so balanced are accepted by the ear as 
equally loud; two tones separately balanced against a third tone prove 
to be in balance with each other. 
