The basic discharger is simply a conductor used to discharge
a Leiden jar. The two arms are spread apart at the hinged joint, and the
insulated handle prevents the operator from receiving a shock as the knobs
are touched against the outer foil and the central knob of the jar.
The two dischargers below are unmarked, and are at Denison
University (left) and Kenyon College (right).
If, on the other hand, the experimenter wants to observe the effect
of an electrical discharge through a body, the universal discharger is used;
five examples are shown below. This is often called Henley's discharger, named,
I think, after William Henley, who developed Henley's
electrometer in 1770. The two electrodes are connected to the electrostatic
machine, and the sample is placed atop the table. Sometimes a slab of ivory
is let into the table top to serve as an insulator. The 1856 Benjamin Pike catalogue
suggests that the apparatus might be used for demonstrations of the oxidation
of metallic leaves between slips of card or of glass, splitting small pieces
of oak and firing gunpowder. An example of the latter demonstration is shown
on the bottom of this page.
University of Mississippi
| At the right is an example of Lane's (or Riess') discharger
in the collection at Washington and Jefferson College.
This device, which is not set up properly in the picture,
is used to deliver constant amounts of charge from a Leiden jar. Thus,
a fully charged jar can deliver a whole series of charges of equal size
to a system.
The picture below, from Linnæus Cumming, "Electricity
Treated Experimentally" (Rivingtons, London, 1886), pg 146, shows how the
discharger is used to supply constant amounts of charge from a battery
of Leiden jars to a universal discharger.
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