of Physiology_, ix. 408). The signals in Breguet's
instrument were in a circuit, including the screens and batteries of a
gun range. The measurement of time depended on the regularity of
rotation of the cylinder, on which each mm. represented 1/1000 second.

Navez.

In the chronograph of A.J.A. Navez (1848) the time period is found by
means of a pendulum held at a large angle from the vertical by an
electromagnet, which is in circuit with a screen on the gun range.
When the shot cuts this screen the circuit is broken and the pendulum
liberated and set swinging. When the next screen on the range is
broken by the shot, the position of the pendulum is recorded and the
distance it has passed through measured on a divided arc. From this
the time of traversing the space between the screens is deduced. By
means of an instrument known as a disjunctor the instrumental
time-loss or latency of the chronograph is determined. [Sidenote:
Benton.] In Benton's chronograph (1859) two pendulums are liberated,
in the same manner as in the instrument of Navez, one on the cutting
of the first screen, the other on the cutting of the second. The
difference between the swings of the two pendulums gives the time
period sought for. The disjunctor is also used in connexion with this
instrument. In Vignotti's chronograph (1857) again a pendulum is
employed, furnished with a metal point, which moves close to paper
impregnated with ferro-cyanide of potassium. The gun-range screens are
included in the primary circuits of induction coils; when these
circuits are broken a spark from the pointer marks the paper. From
these marks the time of traverse of the shot between the screens is
determined.

Bashforth.

In the Bashforth chronograph a platform, arranged to descend slowly
alongside of a vertical rotating cylinder, carries two markers,
controlled by electromagnets, which describe a double spiral on the
prepared surface of the cylinder. One electromagnet is in circuit with
a clock, and the marker actuated by it marks seconds on the cylinder;
the circuit of the other is completed through a series of contact
pieces attached to the screens through which the shot passes in
succession. On the gun range, when the shot reaches the first screen,
it breaks a weighted cotton thread, which keeps a flexible wire in
contact with a conductor. When the thread is broken by a shot, th