Tag Archives: antique instrument collection

Armstrong Treasure Hunt: Wimshurst Machine

Written by Mike Lally ‘18

If one were to walk around Bicentennial Hall, one could see strange contraptions, ranging from one foot high to three feet all, behind glass that appear to be large discs with mallets attached.

Wimshurst Machine

Could these bizarre items be unusual clocks? Perhaps they were used in auditory demonstrations. After all, couldn’t the mallets bang on the disc as a musical instrument? No, the purpose of these machines was not to create sound, but electrical charge.

A device such as this is known as a Wimshurst machine. Invented in the 1880s by James Wimshurst, they belong to class of machines called electrostatic generators. Unlike other apparatus that create an electrostatic spark, a Wimshurst machine does so using induction rather than friction.

The two insulated discs rotate around, often by a mechanical crank, passing by neutralizer bars and brushes. Charges are induced onto the discs and collected onto the combs near the surface of the discs. The charges increase exponentially until the dielectric breakdown voltage of air is reached. When this occurs, a spark is created. The jars are Leyden jars, an early type of capacitor, and act to increase the accumulated charge.

This machine, although able to show the effects of electrostatic charges, can be put to other uses.


Professor Ernest C. Bryrant demonstrating how to operate this Wimshurst machine to students in a physics lab (c.1934).

By connecting it with a chain to an electrostatic orrery, such as that in the 5th floor display of BiHall, one can observe the charges actually turning the orrery. Indeed, there are quite a few electrostatic machines that are within the Middlebury Antique Science Collections that could be connected to a Wimshurst machine for amusing and educational demonstrations.
Wimshurst machines at Middlebury College can be found on the 5th floor of BiHall and in Armstrong Library.

Armstrong Treasure Hunt: Quadrant Electrometer

Written by Mike Lally ’18

While organizing and cataloging the Science Antiques Collection Wendy and I came across a wooden box, standing about a 18 inches high and 10 inches deep.

Elliot’s Quadrant Electrometer

Inside was a mechanism that appeared to be a brass structure inside what can only be described as a birdcage. The item slides out of its carrying case on a wooden platform, which can be removed and the piece therefore is able to be lifted out of its home.
This is a Quadrant Electrometer, made by Elliott Bros. of London in the 1880s. It is a form of an electroscope, which allows more absolute measures of electrostatic potentials. This measures the presence and magnitude of a charge. When a device is attached to the contacts at the base of the machine, the needle floating inside points to the magnitude of the potential.
This machine would have been used within a classroom setting, with students learning about electrostatics. Additionally, the aesthetic qualities of this object indicate that along with its practical use, an artistic use emerges as well. One can imagine such a machine sitting in the parlor room in the late nineteenth century, guests staring at the item while its proud owner explains the machines use and provenance, yet admiring the beauty of object.
This and more aesthetically pleasing scientific instruments can be found in the 5th floor display in Bicentennial Hall.

Armstrong Treasure Hunt: “Philosophical Beads”

On the first day of cataloging the vast array of equipment held in Bicentennial Hall, I came across a small wooden box. Inside the silk lined box are 31 hand blown glass beads with number painted on in gold paint, and a bone slide rule. Engraved on a small ivory plaque on the lid of the box are the words “Lovi Edinr Patentee.” After Wendy informed me that Edinr stands for Edinburgh, I quickly googled to find that they are aerometrical, or specific gravity, beads. Beads such as these, also known as “philosophical beads”, were invented by Alexander Wilson of Glasgow in the 1750s, and were used to determine the specific gravity of a fluid. The user would drop the beads into a liquid until finding the one with neutral buoyancy, which would indicate the specific gravity. By using the slide rule, one could then, for example, find the alcohol content in wine.

These beads turned out to be quite rare. These beads are an improved version, patented by Isabella Lovi in 1805. They presumably were handmade by Lovi, with only four, now five, known sets in existence. After further digging, we discovered that these beads were likely purchased by Professor Hall in 1809 during his trip in Europe, and were used in his lectures at Middlebury, as referenced by student Jonas Colburn in his 1815 notes. We are currently contacting the National Museum of Scotland, which owns other known sets, for more information.

-Mike & Wendy