﻿890 Prof. Barton and Mr. Kilby on Simultaneous 



spot. This is an example of what holds throughout the 

 work, that where few records are presented for any string, 

 the others were of very small amplitude. For each string 

 the effects of ten or more excitations were examined and 

 often plates exposed for all. 



Fig. 30, showing the effect of bowing the A-string, gives 

 a very curious curve for the air's motion. This is partly 

 due to the failure of the spot in this case to move quite 

 vertically. 



The remaining three figures, 31-33, deal with the E-string 

 bowed, the various other modes of excitation showing very 

 little motion by the ordinary method of shooting then in 

 use. As, in this string, bowing at ^ and at \ gave very 

 small motions of the spot, bowing at go was tried. But 

 this (fig. 31) gave such a violent motion of the mirror, that 

 the spot failed to move strictly in a vertical line. This 

 accounts for the curve on the record being slightly undercut. 



Comparison of Records for Clamp and Belli/ Mounting. — 

 Glancing broadly over the two series, figs. 1-22 and 23-33, 

 we see that the former gives simpler curves of larger 

 amplitudes than the latter. Passing to a detailed comparison 

 we may notice that some excitations of particular strings 

 shown in the first set are not represented in the second, 

 although the attempt to obtain these was made. 



As to the interpretation of each set, we may note that the 

 second smaller series (figs. 23-33) obtained with the belly 

 mounting probably gives more strictly the pulsations of the 

 air in the sound-hole relative to the surrounding part of the 

 belly. 



But the figures of the former set (figs. 1-22) obtained 

 with the mirror mounted on the bracket clamped at the 

 corner are of interest as perhaps giving more nearly the 

 effects heard. For, since the corner of the violin in question 

 is very inert, the motion of the membrane with respect to it 

 probably represents the vibrations of the air originated by 

 that part of the violin and thence reaching the hearer. 



Initial Motions. — The photographs taken under the special 

 conditions of shooting to record the initial motions are 

 given in figs. 31-61 of PL XV. Of these, ten (31-43) deal 

 with the G-string, four with the D-string, and of the 

 remaining figures seven each deal with the A-string and 

 E-string. 



Owing to the plate being held in position ready for the 

 excitation of the string, strong lights are shown on the 

 prints just where the holes occurred in the diaphragm. 



