366 



Mr. Charles Tomlinsoris 



sector of the glass contributes the same tone, as may be 

 shewn by employing coloured water in the glass, and, 

 during vibration, applying the finger to the three centres 

 of vibration, as indicated by the fans ; the 4th Sector will 

 continue to vibrate the same note, but will be entirely 

 divested of the fulness, richness, and intensity of the tone, 

 contributed by the isochronous action of the four sectors. 

 It requires some tact to perform this experiment success- 

 fully ; but, when performed, it supports the view we have 

 taken of the production of the various tones. This result 

 is also obtained by the spontaneous action of the glass itself, 

 such a one as the cylinder above-mentioned. During the 

 production of the notes dependent on 10 and 12 nodes, I 

 have not been able to obtain a corresponding number of 

 fans, the places where they ought to have appeared being 

 vacant, and the water perfectly tranquil. This indicates a 

 decided difference between the intensity of the vibration of 

 different sectors of the same glass, where, in one case, out 

 of 10 sectors only 7 vibrated with sufficient force to move 

 the water; and, in the other case, out of 12 sectors, only 8 

 produced fans. The following figure will serve to shew the 

 appearance of the water when the glass was yielding a very 

 high secondary tone due to dodecagonal nodal division. 



Pie. l. 



A, indicates the point at which the bow was applied ; and 

 it is singular, that on one side of it there are five fans, 

 and on the other only two. This imperfect figure, it must be 

 understood, was obtained from the large cylinder : from 

 smaller vessels the 10 and 12 fans can be obtained perfect 

 and without difficulty. 



