Sounding of tivo Notes. 419 



. 6. A series of eleven tuning-forks for notes between b" r and 

 c IV , and a series of nine tuning-forks for notes between 7936 v. s. 

 and c v (8192 v. s.), with prongs 14 millims. in breadth, and 

 below about 8 millims. in thickness. 



7. Three pairs of resonators to strengthen the notes from 

 C to c" y provided with clamping-screws, so that they may 

 with the greater precision be tuned to each note which re- 

 quires reinforcement. They are made of brass, and mounted 

 on iron frames. At the opening of- each of these resonators 

 two side plates can be applied, in case the tuning-forks can- 

 not, in consequence of their weights, be brought near enough 

 to the opening, and it is desirable to lose as little as possible of 

 their action on the body of air. Besides this, each clamp, 

 close to the screw which goes through and moves it, is bored 

 through, and provided with a small pipe, which is generally 

 closed, but which can be opened, in order that by its means, 

 with the help of an india-rubber tube, the ear may be put in 

 direct communication with the body of air within the resonator. 



The two resonators which reinforce the notes from C 

 to g are 30 centims. in diameter, 1 metre 15 centims. in 

 length, and the opening in front is 27 centims. long and 

 12 centims. broad. The two resonators which can be tuned 

 from C to g' are 25 centims. in diameter, 50 centims. in 

 length, and their opening is 23 centims. in length and 7 

 centims. in breadth. The third pair of resonators reinforce 

 the notes from g to c" . Their length is 36 centims., their dia- 

 meter 25 centims., and their opening is 15 centims. in length 

 and 7 centims. in breadth. 



I. Primary Beats and Beat-Notes. 



A. Intervals with the fundamental note C ( = 128 v.s.). 



If at the same time with the deep, simple, and strong note 

 C (128 v. s.), produced by means of a large tuning-fork placed 

 in front of a resonator, a second note is produced in the 

 same manner, which, starting from unison, is gradually raised 

 higher and higher, the beats which ensue after the disturbance 

 of the unison become gradually quicker. When the higher 

 note has reached to 152 or 156 v. s. (that is, between D and E), 

 the beats, which till then were heard separately to the number 

 of twelve to fourteen, change to a roll, which increases in 

 rapidity till the interval of the fourth is nearly reached, about 

 171 v. s. (twenty-two beats), without losing its simple character. 

 When the fourth is passed, there occurs a confused but always 

 very loud rattle, which lasts till above the fifth, until when close 

 upon the sixth, at about 212 to 216 v. s., it begins to lose its 



2 F 2 



