462 Prof. Barton and Mr. Ebblewhite on 



Figs. 6 and 7, on the other hand, where the harsher treat- 

 ment is used, show a marked difference in behaviour of both 

 string and bridge. It is noticeable that figs. 1-11 all deal 

 with the motions of a corner of the bridge due to the strings 

 most remote from it. The other strings when bowed or 

 plucked scarcely move this corner vertically, but did so to a 

 slight extent if struck. These results are given in figs. 12-14. 



Vertical Motion of G-string corner of Bridge. (Lower part 

 of PL VIII.)— Figs. 15-17, for the G-string bowed, by their 

 close similarity, give another proof of the satisfactory working 

 of the apparatus. The string has again only a moderate 

 vertical amplitude and shows the two-step zigzag, while 

 the bridge's motion is large and of striking character. 

 Figs. 18-23, in which the G-string is struck or plucked, 

 again show the rounded curves instead of the sharp peaks 

 always present when the string is well bowed. 



With this comer of the bridge it was again found that no 

 considerable vertical motion could be produced by any but 

 the G-string, the E string giving nothing appreciable. 

 The D and A strings were also ineffective when plucked. 

 Figs. 24-2C) give the best results obtained for the D-string, 

 and figs. 27 and 28 for the A-string which was only effective 

 when bowed. 



Longitudinal Motion of E-string corner of Bridge. (Upper 

 part of PL IX.) — Figs. 29 and 30 are not, like most of the 

 others, true displacement-time curves, because we here failed 

 to secure a simple vertical motion of the spot of light on the 

 plate. Hence the abscissse which should denote time simply 

 are here complicated by the horizontal component of the spot's 

 motion. In other words, the axes are now oblique instead of, 

 as usual, rectangular. Figs. 32 and 33, showing the effects 

 of bowing the A-string, are closely analogous to figs. 27 and 28 

 produced by the same excitation. Fig. 37, in which the 

 A-string is plucked, shows a striking vibrational curve much 

 slower than that of the string and apparently due to some 

 vibration of the instrument as a whole. This is interesting 

 in the light of a similar phenomenon noticed recently by 

 Mr. G. H. Berry in work on the sound-board of the piano- 

 forte (Phil. Mag. April 1910). Other examples of this slow 

 vibration in the present work occur in figs. 31, 50, 60, 66, 

 and 71. 



Figs. 38 and 39, in which the D-string was bowed, show a 

 moderate motion of the bridge though the string is scarcely 

 moving vertically. It may, however, have had a fair hori- 

 zontal motion, which is of course unrecorded by the photo- 

 graph ; indeed it is obviously difficult to produce by bowing 



