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Electric Whirl and Chime combination
This is a demonstration device showing two aspects of electric charge. When the conducting sphere atop the vertical stand is charged (e.g. by using a Leyden jar) the horizontal pinwheel device at the top begins to spin as charge is leaked from its…
Magdeburg Hemispheres
The Magdeburg hemispheres are a pair of large copper hemispheres with mating rims. When the rims were sealed with grease and the air was pumped out through the valve below the lower hemisphere, the lowered pressure within the sphere made it very…
Telegraph
The telegraph was invented by the artist and scientist Samuel Finley Breese Morse (1791-1872), who conceived the idea of the printing telegraph during an ocean voyage to Europe in 1832. The actuation of an electromagnet in the receiver would cause a…
Tangent Galvanometer
The tangent galvanometer is a current measuring device. It was first described in an 1837 paper by Claude-Servais-Mathias Pouillet (1790-1868), who later employed this sensitive form of galvanometer to verify Ohm's law. To use the galvanometer, it is…
Revolving Bell Engine
This was a popular piece of demonstration apparatus, in which the operation of the motor is signaled by a ringing of the bell. The instrument is an inverted revolving electromagnet, with a gearing system added to strike the bell every hundred…
Froment Motor, or Revolving Armature Engine
In 1844 Froment devised an electric motor that was one of the first used for industrial purposes. In his design, electromagnets are energized to attract iron bars mounted on a revolving cage. Once the iron bar is level with the electromagnet, the…
Decade Box, or Variable Resistance
A five decade variable resistor made by Max Kohl of Chemnitz. The 0.1 and 1 ohm resistors are slide wires along the front and back of the top, and the three upper ranges use coils of low-temperature coefficient resistance wire (probably constantan).…
Achromatic Prism
The three prisms hanging from the brass stand may be folded up in pairs to demonstrate achromatism (no color separation) or constant deviation (no color dependence of the angle of minimum bending of light.) These were made by Lerebours et Secretan of…
Movable Planispheres of the Heavens at Every Minute
NOT YET LOCATED.
The description below is not for these exact items. It belongs to a very similar item, which might nonetheless be helpful to the viewer. This cardboard aid for astronomy students was published by Henry Whitall, 512 Arch Street,…
Newton's Rings
This device demonstrates “Newton’s Rings,” colorful interference fringes caused by a thin air layer first discussed by Isaac Newton in a communication to the Royal Society in December 1675, and presented an expanded account in his book "Optics"…
Electric Motor
The label of this electric motor notes that it is a 1/6 HP, 130 Volt motor made by the Crocker Wheeler Motor Company of New York. The patent dates are May 5 and September 22, 1891.
Medical Coil
NOT YET LOCATED.
The effects of electricity on the body can be traced back to 1745 when Pieter van Musschenbroek, testing out the one of the first Leiden jars, stated that "I felt myself struck in my arms, shoulders, and breast. I lost my breath, and…
Kohlrausch Bridge
Friedrich Wilhelm Georg Kohlrausch (1840-1910) was a professor of physics at Göttingen, Zürich, Würtzburg, Strasbourg and Berlin during his career. He wrote a widely-used book on methods of experimental physics, and developed improved measurement…
Jamin's Divided Circle
This apparatus is listed in the 1885 catalogue of Jules Duboscq of Paris as the “Grand Circle of MM. Jamin et Sénnarmont.” It was designed for the study of the laws of polarized light reflected from crystalline substances, from liquids and from…
The Ruhmkorff Coil, or Induction Coil
This late 19th century instrument is often called a Ruhmkorff coil, after the Parisan apparatus manufacturer Heinrich Daniel Ruhmkorff (1803-1877). Although he did not invent the induction coil, his name is often associated with it (particularly in…
Heliostat
The heliostat takes light from the sun as it tracks across the sky, and redirects it in a fixed direction. To accomplish this, the light is reflected from a mirror that reproduces the motion of the sun, except at twice the rate. Although he did not…
Glass Presses
Glass, when stressed, shows the property of double refraction: light of differing polarization directions bends differently passing through the glass. When placed between crossed polarizers , bands of color may be seen, with the spacing of the bands…
Galvanoscope
NOT YET LOCATED.
The term “galvanometer” is in current use, naming an instrument which indicates the strength of an electric current. The Galvanoscope is an earlier instrument, which shows the presence of the current but gives only a rough…
Electric Whirl
In the nineteenth century almost all power supplies were direct current (DC). In order to step voltage up or down, the direct current had to be converted to alternating current (AC), stepped using transformers, and then converted back to DC. The…
Differential Thermopile
NOT YET LOCATED.
When two wires made of different metals are connected to make a loop, and the two junctions between the wires are held at different temperatures, a voltage is produced and electrical current can be detected with a sensitive current…
Current Balance
A current balance measures the force of repulsion between two wires, each carrying an electric current. An upper wire is fixed in place, and the wire directly below it is free to move. The currents are adjusted so that the electrical attractive force…
Thacher's Calculating Device
This early relative of the slide rule has a cylinder 4 in. in diameter and 18 in. long that rotates and slides in and out between the array of twenty equally-spaced parallel bars. The bars have a scale with numbers spaced logarithmically, as on a…
Bladder Glass
This is a device used to demonstrate the effect of atmospheric pressure. A glass vessel with openings at the bottom and top has its large top opening covered by a piece of animal bladder that is tied to seal it around its edges. As air is pumped from…
Arc Light Control
Lightning is the ultimate arc lamp, and so Benjamin Franklin's 1752 experiment of drawing electricity from the clouds and jumping a spark is perhaps the first arc lamp. In 1801 Humphry Davy observed the brilliant spark obtained when the connection…
Ammeter
An ammeter is a device for measuring electric current. The analog ammeter is constructed so as to pass only a small (but known) fraction of the current to be measured through the meter movement that deflects the needle. This allows a very sensitive…
Rotator
Many pieces of demonstration equipment must be rotated to show a desired effect. A Rotator is a device with a crank that can rapidly rotate a small horizontal platform about an axis. Other pieces of equipment, like Newton’s Color Wheel, attached to…
Absorption Cell
These glass spheres were used to contain gases such as iodine, bromine, and hypo-nitrous acid in order to study their light-absorption properties, i.e. their absorption spectra. Light shown on the cell passed through the glass and was absorbed by the…
Voss Machine
In this machine a fixed plate of glass has two metallic foil sectors glued onto it. The slightly-larger rotating plate has six foil dots with raised studs glued to it; the foil sectors are large enough so that two of the studs are opposite each…
1,000 Negroes Wanted.
Newspaper advertisement placed by Brownsburg resident William Taylor seeking to purchase 500 slaves of each gender for sale in the southern market.