ob tamed from a Monochord Sound-box and String. 155 



the string is here distinctly less than half a wave. In the 

 previous figures it was slightly more than half a wave. The 

 frequency of the string was of the order 120 per second. It 

 was bowed at 90 cm. and observed at 44' 5 cm. The leg of 

 the optical lever rested on a glass plate cemented on the head 

 of a pin stuck in the belly at 50' 5 cm. 



Figures 8 & 9 give two photographs taken in quick 

 succession, and quite undesignedly afford an interesting 

 comparison between the analysis by the ear and that by the 

 present graphic method. The circumstances are as follows: — 

 It was desired to obtain curves for the bowing of the string 

 at one-third of its length. But at the instnnt of shooting the 

 first plate, both experimenters noticed that the bowing was 

 bad and the tone produced of a " whistling " character. This 

 was entered in the notebook, and a second plate exposed under 

 similar conditions without stopping to develop the first. 

 The second plate was shot while the tone was recognized by 

 both observers to be of fair quality, considering the place at 

 which the string was bowed, the best musical tone being of 

 course impossible under those conditions. The difference 

 thus heard and noted is clearly exhibited in the two negatives. 

 The earlier one, figure 8, shows crinkles in the string's curve 

 which are almost entirely absent from the second, figure 9. 

 The curves for the belly also show a like difference. The 

 curve for the belly's motion in figure 9 consists almost solely 

 of components of frequencies 1 and 3. Now if the bowing- 

 had been exactly at one-third of the length, the third partial 

 should have been absent. But, as is known, a slight deviation 

 in the place of bowing would bring out the partial in question 

 very strongly. The frequency of the string in these figures 

 was 114 per second. It was bowed at 66£ cm. and observed 

 at 44*5 cm. The leg of the optical lever was on the glass- 

 headed pin at 50'5 cm. 



Figure 10 illustrates the entirely different motions produced 

 in string and belly by plucking. The frequency of the string- 

 here was 128 per second. It was plucked by finger and 

 thumb at 85*7 cm., i. e., at one-seventh of its length, and was 

 observed at 44'5 cm. The leg of the optical lever was on the 

 glass-headed pin at 50 "5 cm. 



Figure 11 illustrates a strikingly simple motion of the belly 

 when the string was pitched higher than before. It had in 

 this example a frequency of 153 per second. It was bowed 

 at 90 cm. and observed at 44*5 cm. The leg of the optical 

 lever was resting on a glass-headed pin at 50*5 cm. The 

 curve for the motion of the belly is easily found to consist 

 chiefly of components of relative frequencies 1 and 2, whose 



