ends are wound round the wrest-pins, which are inserted in the wooden
bed, called the wrest-plank, the strength and efficiency of which are
most important for the tone and durability of the instrument. It is
composed of layers of wainscot oak and beech, the direction of the
grain being alternately longitudinal and lateral. Some makers cover the
wrest-plank with a plate of brass; in Broadwood's grands, it is a plate
of iron, into which, as well as the wood, the wrest-pins are screwed.
The tuner's business is to regulate the tension, by turning the
wrest-pins, in which he is chiefly guided by the beats which become
audible from differing numbers of vibrations. The wrest-plank is
bridged, and has its bearing like the soundboard; but the wrest-plank
has no vibrations to transfer, and should, as far as possible, offer
perfect insensibility to them.

I will close this introductory explanation with two remarks, made by the
distinguished musician, mechanician, and inventor, Theobald Boehm, of
Munich, whose inventions were not limited to the flute which bears his
name, but include the initiation of an important change in the modern
pianoforte, as made in America and Germany. Of priority of invention he
says, in a letter to an English friend, "If it were desirable to analyze
all the inventions which have been brought forward, we should find that
in scarcely any instance were they the offspring of the brain of a
single individual, but that all progress is gradual only; each worker
follows in the track of his predecessor, and eventually, perhaps,
advances a step beyond him." And concerning the relative value of
inventions in musical instruments, it appears, from an essay of his
which has been recently published, that he considers improvement in
acoustical proportions the chief foundation of the higher or lower
degree of perfection in all instruments, their mechanism being but of
secondary value.