ACOUSTICS. 73 



not quite in unison, the same experiment will give the 

 scroll of irregular amplitude, (Fig. 52). 



Fig. 52. 



Remove the slides from the short fork and fix them 

 upon the long one near the end, and, if necessary, at- 

 tach two pairs, and adjust them so that the ratio of vi- 

 brations is as 2 to i ; that is, their pitch is an octave 

 apart. The resulting figures are shown in Fig. 53 ; and 



when the forks are tuned exactly, the figure first de- 

 veloped will remain, with no other alteration than a 

 decrease in size, and may be a parabola, an 8> called 

 a lemniscata, or an intermediate form. 



While this figure 8 is upon the screen let the second 



X'iy. 64. 



fork be rotated through a small arc, as before with the 

 unison, and the scroll shown in Fig. 54 will appear. 



By trial the slides may be so adjusted upon one of 

 the forks that all the varying ratios in the octave may 

 be obtained. The simpler the ratio the simpler the 



