E&M-S 6: The large electrostatic machine
Equipment: large electrostatic machine in Room 2, between Rooms 3 and 5.
Procedure:
"This machine is of the Toepler-Holtz design and comes from
the late 1890's. It was sold to practicing physicians as a potential
source for the excitation of X-ray tubes. For this it works quite well,
yielding about 1 mA at 80 kV at moderate rates of rotation. Accessories
to be found in the drawers are for `electrical treatment` for such things
as baldness, lameness, etc. Most are systems of points designed to produce
brush discharges. A low table with glass legs is included for electric
isolation of the patient. Some of the devices look as though they are
instruments of torture even without the application of electricity. The
case enclosing the plates should not be opened except for repairs. In
no case should the inside of the case or the works be cleaned. This was
done by WPA workers without our permission and it was three years before
we could get all the conducting films they deposited satisfactorily removed.
Even yet the peak voltage of the machine is about 80% of what it was before
the catastrophe. In the deep depression this machine was purchased from
the late Dr. Snyder of Roland, Iowa for $25 when he closed out his downtown
office.
"The machine is operated by turning the crank counterclockwise as one
looks at the front. A rotary switch at the center connects or disconnects
the Leyden jars to the terminals. If there is difficulty starting the
charge separation, use the hints given for the small influence machine.
Under severely adverse conditions you may have to connect the small machine
terminals to those of this machine to get sufficient charge for starting.
Do not allow the machine to be turned at high speed. The mechanical balance
is far from perfect and injury to the glass plates can easily result.
"On one terminal is a mass of paper ribbons which are slightly conducting.
When the potential of this terminal has been high for a sufficient time,
these ribbons become charged alike and repel each other.
"Store the machine with the spark gap closed, perhaps with the belt off
one of the pulleys." - Percy Carr (1970)
In the drawers are also some photocopies of selected pages from two old
books (available in the ISU library) showing how this machine was used in
medical practice.
"In the early 1990s the Iowa Board of Regents was asking faculty members to
warn students in advance when they were planning to have classroom activities
which might be controversial; this was prompted by the showing in a
University of Iowa class of a film that some students found offensive.
As a humorous protest against this directive, I would then introduce this
demonstration by telling the students that if they or their parents or
other relatives or any of their loved ones were doctors, or were planning
to become doctors, they might want to leave the room to avoid offense at
what I would be showing them next. Of course, no one ever left and everyone
became very attentive. I would then demonstrate this apparatus and read
some of the ridiculous claims for it made in old medical textbooks, ending
by pointing out that while it is easy to laugh at the gullibility of
patients in the early part of this century who believed in the efficacy of
this arcane equipment, patients today pay enormous sums to doctors and
hospitals for still more sophisticated equipment and tests today, and we
may someday look back at some of this and laugh." - Laurent Hodges (1994)