86 Mr White, The Origin of the ‘ Wolf-note’ ‘ 
By means of adjustable clamps attached to the rod the instrument 
could be securely fixed. At the spot on the belly chosen for 
investigation a strip of wood covered with a piece of microscope 
cover glass was fixed. This formed a support for one leg of the 
optical lever. The other two legs rested in a conical hole and 
V-groove made in a bracket attached to the edges of the belly 
and back (the edges joined by the ribs are practically free from 
vibration). The optical lever was kept with its legs horizontal 
and in contact with the belly and the bracket plate by means of 
two rubber bands. The mirror of the optical lever was attached 
directly to the plate carrying the legs and therefore rocked about 
a vertical axis. A beam of light from a pin-hole illuminated by 
an arc lamp was directed on the small concave mirror and focused 
on the photographic plate. Half plates were used and were fixed 
in a dark slide which could drop in a framework. The latter 
could itself be moved horizontally thus allowing ten or more 
exposures to be made on one plate. The dark slide was held at 
the top of the rails by an electromagnet, and at the required 
moment was dropped by breaking the circuit with a lever under 
the experimenter’s foot. The optical lever was placed with its 
movable foot on the C-string side of the belly and near the 
¥-hole. . 
First the author satisfied himself that the main features of a 
re tt ce 
vibration curve however complex could invariably be reproduced - 
on repeating the note. Curves 1—3 (Fig. 2) were obtained by 
bowing the open D-string with different intensities. A slight 
difference in the prominence of partials will be observed. 
Secondly it was ascertained how the character of the vibration 
curve for a given pitch depended on the point examined on the 
belly. Three points on the beily were studied and such small 
differences as were obtained in the vibration curves could be 
completely accounted for by the changes in amplitude. Curves 
4—6 (Fig. 2) were obtained by bowing A on the G-string and 
recording the vibration of a point on the belly (@) near the left 
foot of the bridge, (b) 9 cms. above the top of the left F-hole and — 
(c) 9 cms. below the bottom of the left F-hole. The magnification 
was arranged to suit the amplitude obtained. 
It was also observed that the character of the belly vibration — 
produced by bowing a string was often greatly affected by the 
forced vibrations of the other three strings if these were free to 
vibrate. Curve 7 (Fig. 2) was obtained by bowing the open 
G-string, the other three strings being free; the belly vibration 
changed to that shown in curve 8 on fixing these strings. In the 
following examination of the vibrations produced by bowing a 
string other strings were always fixed. 
Feeling satisfied from the above and similar tests that the 
