e purpose of receiving the electricity from the
glass plate, the arms of the U being held upon either side. The other
ends of the conductors are connected by a rod from the middle of which
projects another rod terminating in a knob, for delivering the spark.

On turning the plate, a faint snapping sound is heard, and when the
room is darkened, a spark is seen to be thrown out from the knob
projecting from the _prime conductors_.

Many curious and interesting experiments may be performed by means of
the machine, illustrating the general properties of electricity. For
instance: a person standing on an insulated bench, that is, a bench
with glass legs, or having the legs resting on glass, and having one
hand on the conductor, can send sparks, with the other hand, to
everything and everybody about. This illustrates communication of
electricity by contact. A wooden head, covered with long hairs, when
placed on the conductor, illustrates electrical repulsion, by the
hairs standing on end.

If the hand is held to the knob, sparks will pass from it in rapid
succession, causing in the hand a sensation of pain. This is called an
_electric shock_, and is caused by the electric fluid occasioning a
sudden motion by the contraction of the muscles through which it
passes. The force of the shock is in proportion to the power of the
machine.

What are the Muscles?

Bundles of thin fleshy fibres, or threads, fastened to the bones of
animals, the contraction and expansion of which move the bones or
perform the organic functions of life.

_Organic_, relating to organs or natural instruments by
which some process is carried on.

_Functions_, employments or offices of any part of the body.

_Contraction_, drawing in or shortening.

_Expansion_, extending or spreading out.

What is Twilight?

The light from the first dawning of day to the rising of the sun; and
again between its setting and the last remains of day. Without
twilight, the sun's light would appear at its rising, and disappear at
its setting, instantaneously; and we should experience a sudden
transition from the brightest sunshine to the profoundest obscurity.
The duration of twilight is different in different climates; and in
the same places it varies at different periods of the year.

_Instantaneously_, done in an instant, in a moment's time.

_Obscurity_, darkness, want of light.

How is it produced?

By the sun's re