or Pflueger's cylinder governed by conical
pendulum); J.G. M'Kendrick, _Life in Motion_ (1892) (for early form of
cylinder chronograph by Thomas Young); Stirling, _Outlines of
Practical Physiology_ (for reaction-time chronographs of F. Galton and
Exner). (2) Chronographs used in gun work and for other purposes:
Sabine, _Phil. Mag._ (1876); Moisson, _Notice sur la chronographie
systeme Schultz_ (Paris, 1875); Paul la Cour, _La Roue phonique_
(Copenhagen, 1878); Mach, "Collected Papers on Chronographs,"
_Nature_, 42, p. 250; C.V. Boys, "Bullets photographed in Flight,"
_Nature_, 47, p. 415; Pneumatic Tube Co., Paris, "Chronograph,"
_Nature_, 9, p. 105; G.C. Foster, "Laboratory Chronograph," _Nature_,
13, p. 139; E.S. Holden, "Astronomical Chronograph," _Nature_, 26, p.
368; D'Arsonval, _La Lumiere electrique_ (1887); Dunn, "The
Photo-retardograph," _Journal United States Artillery_, 8, p. 29; E.J.
Marey, _La Methode graphique_ (for Deprez accelerographe); Werner
Siemens, "Electric Spark Chronograph," _Wied. Ann._ (1845), 66.
(F. J. J. -S.)

FOOTNOTE:

[1] The velocity of the projectile is found thus. Let V be the
velocity of the bob, due to the impact of the projectile, _v_ the
velocity of the projectile, _h_ the height through which the bob is
raised vertically, then

V squared ___
h = --, and V = \/2gh.
2g

If W be the weight of the bob, and _w_ the weight of the projectile,
then

/ W \ ___
wv = (W + w)V, and v = ( --- + 1 ) \/2gh.
\ w /

If _l_ be the true length of suspension, and C the length of the
chord of the arc of displacement of the bob after being struck, then

___
/ W \ / g
C squared = 2hl, and v = ( --- + 1 ) / --- . C.
\ w / \/ l

Also if T be the time of a complete small oscillation of the
pendulum,

___
2[pi] / g
----- = / ---,
T \/ l

/ W \ 2[pi]C
so that v = ( --- + 1 ) ------.
\ w / T

CHRONOLOGY (Gr. [Greek: chronologia], computation of time, [Greek:
chronos]), the science which treats of time, its object being to arrange
and exhibit the various events which have occurred in the