654 



Mr. G. H. Berry on the 



and was slightly curved as is the practice of pianoforte- 

 makers. The bridges are of English Beech. The steel strings 

 used were of No. 18 gauge and weigh 0*062 grm. per cm. 



The straw forming the connexion between the sounding- 

 board and optical lever was in all cases about 5 cm. below 



the bridge. 



Results. 



On Plate XII. are shown 25 photographs. 



Nos. 1-6 give the natural frequency of the different sections 

 of sounding-board used. They were struck with a pianoforte 

 hammer. 



In the following table column A gives the distance of the 

 point struck from the bottom of the section, column B the 

 distance from the right-hand edge, and column C the pitch 

 of the strings on the section. 



Films. 



A. 



B. 



C 







on. 



cm. 







1 



240 



4-4 



A# 



116 



2 



1.35 



30 



c' 



261 



o 



90 



2-5 



c' 



261 



4 



no 



35-0 



2-5 

 5-0 



c' 

 Afl 



261 

 116 



5 



6 



350 



50 



At 



116 





In every case the wave passes immediately from the right- 

 hand edge of the print to the left-hand edge, and in most of 

 the prints the waves somewhat overlap. 



In the first six prints the shutter was set to open at the 

 instant the hammer struck the board. 



With the exception of No. 6 the amplitude falls off very 

 rapidly and the upper partials become more marked as the 

 vibration dies away. In practice, no part of the sounding- 

 board of a pianoforte has so low a frequency as that showu 

 on No. 6. 



In No. 7 the three steel strings were 66*5 cm. long between 

 the bridges and were struck at ^ from the fixed or lower 

 bridge. All the films Nos. 7-25 inclusive were exposed 

 about one second after the hammer had struck the strings. 



The opinion as to the tone is that of a pianoforte tuner who 

 has an exceptionally good musical ear. He did not know 



