uspension is introduced has been used by A.
Mallock, to determine the resistance of the air to bullets having a
velocity up to 4500 F/S. (_Proc. Roy. Soc._, Nov. 1904). A ballistic
pendulum, carried by a geometric suspension from five points, has also
been employed by C.V. Boys in a research on the elasticity of golf
balls, the displacement of the bob being recorded on a sheet of smoked
glass.[1] For further information on the dynamics of the subject see
_Text Book of Gunnery_, 1897, p. 101.

In nearly all forms of chronographs in which the ballistic pendulum
method is not used, the beginning and end of a period of time is
recorded by means of some kind of electrically controlled mechanism; and
in order that small fractions of a second may be measured, tuning-forks
are employed, giving any convenient number of vibrations per second, a
light style or scribing point, usually of aluminium, being attached to
one of the legs of the tuning-fork. A trace of the vibration is made on
a surface blackened with the deposit from the smoke of a lamp. Glazed
paper is often employed when the velocity of the surface is slow, but
when a high velocity of smoked surface is necessary, smoked glass offers
far the least resistance to the movement of the scribing points. If the
surface be cylindrical, thin sheet mica attached to it, and smoked,
gives excellent results, and offers but little resistance to all the
scribing points employed. The period of vibration of tuning-forks is
determined by direct or indirect comparison with the mean solar second,
taken from a standard clock, the rate of which is known from transit
observations ("Recherches sur les vibrations d'un diapason etalon," R.
Koenig, _Wied. Ann._, 1880). In the celebrated ballistic experiments of
the Rev. F. Bashforth, the time markings were made electrically from a
standard clock, and fractions of a second were estimated by
interpolation. Regnault (_Memoires de l'acad. des sciences_, t. xxxvii.)
employed both a standard clock and a tuning-fork in his determination of
the velocity of sound. The effect of temperature on tuning-forks has
been determined by Lord Rayleigh and Professor H. McLeod (_Proc. Roy.
Soc._, 1880, 26, p. 162), who found the coefficient to be 0.00011 per
degree C. between 9 deg. C. and 27 deg. C. The beginning and end of a time
period is marked on a moving surface in many ways. Usually an
electromagnetic stylus is employed, in which a scribing point suddenly
move