right number of hairs, for if the ribbon be too thick
it hinders the vibration of the strings; if too thin the friction is
not strong enough to produce a good tone. Fetis gives 175 to 250 as
the number used in the modern bow,[3] and Julius Ruhlmann 110 to
120.[4] Tourte attached the greatest importance to the hairing of the
bow, and bestowed quite as much attention upon it as upon the stick.
He subjected the hair to the following process of cleansing: first it
was thoroughly scoured with soap and water to remove all grease, then
steeped in bran-water, freed from all heterogeneous matter still
adhering to it, and finally rinsed in pure water slightly blued. When
passed between the fingers in the direction from root to tip, the hair
glides smoothly and offers no resistance, but passed in the opposite
direction it feels rough, suggesting a regular succession of minute
projections. The outer epithelium or sheath of the hair is composed of
minute scales which produce a succession of infinitesimal shocks when
the hair is drawn across the strings; the force and uniformity of
these shocks, which produce series of vibrations of equal persistency,
is considerably heightened by the application of rosin to the hair.
The particles of rosin cling to the scales of the epithelium, thus
accentuating the projections and the energy of the attack or "bite"
upon the strings. With use, the scales of the epithelium wear off, and
then no matter how much rosin is applied, the bow fails to elicit
musical sounds--it is then "played out" and must be re-haired. The
organic construction of horsehair makes it necessary, in hairing the
bow, to lay the hairs in opposite directions, so that the up and down
strokes may be equal and a pure and even tone obtained. Waxed silk is
wound round both ends of the hair to form a strong knot, which is
afterwards covered with melted rosin and hardens with the hair into a
solid mass.

The head, 1 in. long and 7/16 in. wide at the plate, is cut in one
piece with the stick, an operation which requires delicate
workmanship; otherwise the head is liable to snap at this point during
a _sforzando_ passage. The head has a chamber and wedge contrivance
similar to that of the nut, in which the other end of the hair is
immovably fixed. The hair on the face of the head is protected by a
metal or ivory plate.

The model bow here described, elaborated by Fr