An automaton figure, exhibited in London a short time
since, which drew profiles of its visitors, was regulated by a
mechanism on this principle. A small aperture in the wall,
opposite the seat in which the person is placed whose profile is
taken, conceals a camera lucida, which is placed in an adjoining
apartment: and an assistant, by moving a point, connected by a
pentagraph with the hand of the automaton, over the outline of
the head, causes the figure to trace a corresponding profile.
148. By turning. The art of turning might perhaps itself be
classed amongst the arts of copying. A steel axis, called a
mandril, having a pulley attached to the middle of it, is
supported at one end either by a conical point, or by a
cylindrical collar, and at the other end by another collar,
through which it passes. The extremity which projects beyond this
last collar is formed into a screw, by which various instruments,
called chucks, can be attached to it. These chucks are intended
to hold the various materials to be submitted to the operation of
turning, and have a great variety of forms. The mandril with the
chuck is made to revolve by a strap which passes over the pulley
that is attached to it, and likewise over a larger wheel moved
either by the foot, or by its connection with steam or water
power.
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