Franklin-Wistar Friction Machine?
A few years ago, I purchased from
a New York dealer the machine pictured at right. It compares with
a German highly finished electrostatic machine as tramp art to
Chippendale. I was told that it is genre piece probably dating
in the era from 1890 to 1920.
Our machine is very similar with the one in the
second picture which, as very precisely described "was used
by William Hayley, a friend and patron of Cowper, in an attempt
to alleviate the paralysis Mary Unwin suffered after her stroke
in 1792. The use of the machine is further described as "Electricity
was generated by turning the handle of the machine, which caused
friction between glass and silk. It was then transferred through
the metal cylinder and stored in a Leyden jar, from where it was
collected and applied to the affected limb with the use of the
discharging tongs" Amen!
The mechanical model is clear: In Franklin own words,
"We had for some time been of opinion that the electrical
fire was not created by friction, but collected, being really
an element diffused among and attracted by other matter, particularly
by water and metals. We had even discovered and demonstrated its
afflux to the electrical sphere, as well as its efflux" from
I will try below, with images and text, to advocate
that the friction electrostatic machine in our collection was
made by Casper Winstar at the request of Benjamin Franklin. Few
people might have the patience to read my arguments and even fewer
to agree with my points. Overall, this is a good exercise for
me to learn to describe well an antique scientific apparatus and
in the extreme, a hard to believe discovery.
The Leyden jars are partially filled with shavings
of cast iron. No visible oxide on the surface of the grains.
Two point contacts, one milimeter appart on the surface of a
grain, produce less than 10 ohms of series resistance. The smaller,
long neck Leyden jar has two electrodes made-out of iron. One
terminates with a nice spherical head and the other shows some
left over fiber probably used to tide-up there some whiskers.
The leyden jars can be set up close to the glass cylinder during
charging and the "afflux or efflux of electrical fire"
estimated. Furthermore, the pine wooden plank on which the experiment
is set has three unused holes which may indicate that the wood
was used previously for something else. I speculate that the
contraption is not a commercial machine or a kit but a research
apparatus made by people versed in glass blowing under specification
of a scientist studding the "electrical fire".
The two pictures above shows how
the silk or fur was held on the cylinder. Most glass, through
friction, charges positively. The electrons dissipate in air through
the carefully shaped steel wire holder. Initially I thought that
the maker of this machine avoided deliberately any metallic parts,
even nails, except in the Leyden jars and the holder of the rubbing
material. This was not true; in the middle of 18 century, nails
and screws were not yet popular fasteners. The bottle for the
Leyden jars were held, in the last stage of manufacturing, with
a fused glass bar on the bottom. That permitted the glass blower
to achieve a well rounded opening. At the right four bottles attributed
to Gaspar Wistar are shown. Although most of the bottles manufactured
in this era are similar, I speculate that the Leyden jars on our
electrostatic machine are made with Wistar bottles. Recently in
the article "Buttons to Bottles" the author writes:."Wistar
glass also enjoys the historic and scientific honour of having
been made to specification for Benjamin Franklin, who incorporated
Wistar glass in a variety of devices he designed for his experiments
in electricity. Franklin tested his first lightning rod at Caspar
Please see three portable friction machines bellow. The first
one was presented as belonging to Ben Franklin.
To me, the machines in the last rows are commercial
versions of a research friction machine as in NSM collection:
the Franklin-Wistar machine. The only improvement
are the pins on the wheels that permit a more forceful rubbing
and what was learned from Frankin experiments: the comb which
"will effuse electric fire" (provide neutralization
charge for the positively charged glass cylinder and in the
process will charge the Leyden jar).
The one below here, I photographed at Harvard collection; it
is cataloged as "English-made, circa 1800, with 19th century
An almost identical machine, attributed to Thomas Corbett (1780-1857),
Canterbury, N.H., and dated 1810 is pictured bellow. One have
to look for details to observe that indeed the three machine
are not three pictures of the same.
|Please see bellow, auxiliary pictures that may help
in understanding the techniques used in the manufacturing and the
era when this machine was built.
Cast iron (I hope I remember well) has a lower melting point
if the carbon content is higher. Probably, first iron shafts
were machined out of high carbon content cast iron. In the picture
above is the content of the Leyden jars associated with our
electrostatic machine. The neck of the smaller leyden jar shows
the marks left by the forming tool. "punty" marks
on the bottom.
I am grateful to Professor Paselk and Dr. Alistair Kwan who pointed-out
that the lack of nails and the use of pegs is not because the
makers of the machine tried to avoid metals but because by the
middle of 18th century nails were a rare commodity. Slightly embarrassed,
I am happy to see something pointing towards the middle of 18th
"punti" mark can be observed on the base of the large
jar, where a rod was attached during the blowing process.