66 UNIVERSITY OF MISSOURI STUDIES 



seem improbable — so far as our theoretical data permit us to 

 draw a conclusion — that such a sudden, but weak decrease 

 in intensity might become noticeable as a kind of just per- 

 ceptible "beat." I leave it to the reader to decide experi- 

 mentally whether the tone 9 in this combination appears 

 slightly "rough" or perfectly "smooth." 



The tenth and eleventh sections of the partition move 

 down and up six times during the period. But we must 



remember here from our previous discus- 

 Do we hear 6i? sion that — in order to conclude as to the 



tones to be heard — no indiscriminate count- 

 ing is permissible. Mere counting of stimuli would indicate 

 the tone heard only in case it seems probable that these stimuli 

 occur in equal or approximately equal intervals. Now, a 

 survey of figure 23 does not make it appear probable that the 

 stimuli on the two sections in question occur in even approx- 

 imately equal intervals. The partition moves down at F 

 and remains in the lower position until it moves up at I. It 

 moves down at J and immediately, at K, up again. Down 

 at L and up at M. In this upper position it remains until 

 P, when it moves down. At Q it is up again, to stay in the 

 upper position until B, when it moves down. At O it is up 

 again. At D it moves down, at E up, and at F down again. 

 Are we justified in concluding that the nerve ends located on 

 these two sections of the partition must convey to our mind 

 the sensation of the tone 6 of the intensity two; or any other 

 definite sensation? I do not know how to answer this ques- 

 tion. If we knew the time intervals between the successive 

 stimuli exactly, we might attempt to decide whether one or 

 the other sensation would be more or less probable in this 

 case. But we know that figure 23^ is only an approximate, 

 not an exact representation of the actual movement of the 

 partition. It is a certain comfort in this dilemma that the prac- 



