>=‘ Bee 
a 
y 
139 
cians. The precise meaning in which concert pitch ought to 
be understood was then explained, as also the means by which 
instruments ought to be tuned to it. 
Concert pitch is determined by the number of double vibra- 
tions which any string or pipe makes in a given time. The 
apparatus used by the author for ascertaining the number was 
then described: he described the means by which he attained 
a standard pitch. Some experiments were detailed, the cal- 
culations founded on them were entered into, and the results 
stated. The present concert pitch was shown to be at all 
times attainable and recoverable by throwing a steel wire of a 
certain length, diameter, and tension, into vibration, so that 
it shall quit and return to the point of inflection a certain 
number of times, within a given period. 
Calculations and processes were then entered into, for ob- 
taining the proper wire at all times, in case of its being no 
longer manufactured or sold. Means of proving or testing 
its qualities, and examples, were given. Necessity of great 
precision in these processes was proved by the instance of 
wires differing in diameter by the one-thousandth part of an 
inch, sounding notes which differed by very nearly a semitone. 
The errors of Mersenne in attributing the pitch of bells to their 
composition, and in estimating the effect of the component 
_ metals, were noticed. Similar mistaken notions were shown 
_ to have been acted on by the makers of piano-fortes. 
" The Rev. Professor Dixon exhibited a model intended to 
__ illustrate the azimuthal motion of a freely suspended pendu- 
lun, of which he gave the following account : 
** This model is constructed on the principle, that we may 
consider the parallel of latitude, along which the point of sus- 
pension of the pendulum is carried by the diurnal rotation, to 
be made up of a number of elements, each of which coincides 
with the corresponding element of a great circle tangent to 
i 
