Washington and Lee University

Washington and Lee University Washington and Lee University The University Library

physics apparatus at washington and lee : a selection of teaching instruments

Information borrowed from Thomas Greenslade's website Instruments for Natural Philosophy.

Thanks also to Prof. Emeritus Tom Williams of the Physics Department at W&L.

 

absorption cell

Absorption Cell

These glass spheres were used to contain gasses such as iodine, bromine, and hypo-nitrous acid in order to study their light-absorption properties, i.e. their absorption spectrae. Light shown on the cell passed through the glass and was absorbed by the gas differentially at different wavelengths. The spherical cells are listed in the 1888 "Illustrated Catalogue of Instruments used in Physical Optics" published by James W. Queen and Co. of Philadelphia at $7.00.

 

Optics

rotator

 

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 the platform of the Rotator for the purpose of demonstration.

 

Mechanics

ammeter

 

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 measuring device to safely measure large currents. The basic mechanism was developed by Edward Weston in the last few years of the 19th century. Analog ammeters have been almost entirely replaced in the last two decades by digital current meters.

 

Electrical Measurements

 

arc light control

 

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 between two carbon rods, attached to the poles of a battery, was broken. Some years later, in a demonstration lecture at the Royal Institution, he produced an arc nearly three inches in length. He used a voltaic battery with 2000 sets of plates, each four inches square. Commercial arc lighting had to wait for the development of dynamos such as the Gramme Machine in the early 1870s.

Greenslade category: Electricity

bladder glass

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 the vessel through the bottom opening, atmospheric pressure causes the bladder to deform downward, ultimately bursting with a loud bang. This seemingly simple effect is mentioned in the majority of nineteenth century physics textbooks.

Pneumatics

thachers calculating device

 

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 slide rule’s multiplication scales. The cylinder also has a logarithmic scale engraved lengthwise on it. The net effect is that of a very long slide rule, allowing calculations accurate to four to five digits to be made. In 1934 this instrument was sold by Keuffel and Esser for $80.00.

Calculating Devices

current balance

 

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 on the lower wire perfectly balances the gravitational force on the wire so that the wire levitates, at rest. Weights can be added to the lower current to increase the gravitation force. This device allows one to study the attractive electrical force between the wires as a function of the currents through the wires.

Electrical Measurements

differential thermopile

   

Differential Thermopile (this instrument is missing)

  When a loop circuit is made of two dissimilar metals, and the two junctions between the two wires are held at different temperatures, an EMF is produced and a current can be detected with a sensitive galvanometer. This is the Seebeck Effect, discovered by Thomas Seebeck in 1821. The effect is multiplied when there are a number of junctions in series in the circuit, with alternate junctions in close thermal contact with each other. The use of the root pile mirrors the arrangement of galvanic pairs in a galvanic pile.

  The Differential Thermopile was invented by Macedonio Melloni (1798-1854), an Italian physicist who worked in France and Italy. Melloni's research dealt with thermal radiation, and he developed the thermopile to make quantitative measurements of the intensity of the radiation. 

           Washington and Lee differential thermopiles are by E.S. Ritchie. The model with 20 pairs of junctions sold for $25.00 in the 1881 catalogue; for $40.00 you could get the 49 pair model. With an end-cap covering one set of thermo-junctions, the differential thermopile could be used to study, for example, the reflection of thermal radiation or the inverse-square law.
 

Heat

electric whirl

       

Electric Whirl

The Electric Whirl or Electric Fly is a static electricity demonstration device. It features a star-shaped horizontal “propeller” at its top, made of a number of brass wires, with rearward-facing sharp points. This is balanced atop a conducting shaft. When the device becomes electrically charged, the charge will leak off into the air at the sharp points. The leaked charges repel the points that emitted them since both have the same sign of their electrical charge, and the horizontal Whirl begins to rotate, somewhat like a rotary water sprinkler.

Static Electricity

electrotome

 

Electrotome

An induction coil is a step-up transformer, and so requires an alternating current input to the primary. In the nineteenth century almost all power supplies were direct current, and so a way had to be found to convert DC to AC. The standard technique was a mechanical interrupter or Electrotome, run at a frequency controlled by the mechanical attributes of the device. 

This interrupter was made by Morris E. Leeds & Co of Philadelphia, "Manufacturers of High Grade Electrical Measuring Instruments, X-Ray Equipment and other Scientific Apparatus". The date is no later than 1900-1902. 

Electricity

froment motor

Froment Motor

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 current to the electromagnet is cut off until the next iron bar is in range. A commutator is used to complete and then break the current to the electromagnet. This Froment-type motor was probably made in the second half of the 19th century.

Electric Motors

galvanoscope

 

Galvanoscope (instrument is missing)

We are accustomed to the word galvanometer, which indicates the strength of an electric current. The Galvanoscope is an earlier instrument, which shows the presence of the current and gives only a rough indication of its magnitude 

  The basic galvanoscope has only a single turn of wire to set up the magnetic field which turns the magnetic needle. It can be made more sensitive by increasing the number of turns of wire in the loop surrounding the needle. This was first done (in quite different ways) by J. S. C. Schweigger (1779-1857) in 1820 and J. C. Poggendorf (1796-1877) in 1821. Schweigger's method was to wind several turns of copper wire around the compass case. The multiple-turn coil was termed a multiplier because it multiplied the effect of the single turn on the needle. 

?

This galvanoscope, at Washington and Lee University, was made by Benjamin Pike, Jr. of New York, and is listed at $3.50 in the 1856 second volume of Pike's catalogue. Note that it is listed by Pike as a galvanometer. There is a similar instrument at Colby College.

Electrical Measurements

glass press


Glass Press

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 being correlated to the amount of stress present at a particular point: small spacing indicates large stress.

Polarized Light

heliostat

 

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 invent the heliostat, the Dutch physicist William Jacob s'Gravesande gave it first prominence through mention in his 1742 textbook by. He coined the word from the Greek words for “sun” and “stationary.” This is a Silbermann-type heliostat made by Duboscq.

 

Optics

induction coil

The Rhumkorff Coil

Late 19th century.

This sort of coil 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 Europe) because he successfully put together all of the elements of the coil, including the use of the condenser connected across the primary to moderate the back EMF of the collapsing magnetic field of the secondary.
 

Electricity

jamin's divided circle

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 metals. It could also be used to measure indices of refraction. With its accessories it cost 1000 francs (about $200). The circle is an early example of an ellipsometer, used to study the reflection of light at or near Brewster's angle.

 

Polarized Light

kohlrausch bridge

 

Kohlrausch Bridge

This instrument can be found in the 1921 catalogue of E. Leybold's Nachfolger [Successors] of Cologne at a price of $38. The text reads: "Kohlrausch's universal bridge, allowing of reading the resistance of wires and electrolytes in ohms, with induction coil and 5 coils of 0.1, 1, 10, 100, 1000 ohms for comparison, available for resistances from 0.05 to 20000 ohms."  Friedrich Wilhelm Georg Kohlrausch (1840-1910) was a professor of physics at Göttingen, Zürich, Würtzburg, Strasbourg and Berlin during his career.

Electrical Measurements

medical coil

 

Medical Coil (instrument is missing)

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 it was two days before I recovered from the effects of the blow and terror."

   Early treatment with electricity used shocks delivered by Leiden jars or condensers, but after the discovery of electromagnetic induction by Michael Faraday in 1831 it was possible to deliver shocks using specialized Magneto-Electric Machines. In both cases bobbins wound with many turns of fine wire revolved in the magnetic field of a U-magnet. In the machine from the Smithsonian this magnet appears to be missing, but the fanciful metal-work certainly has visual appeal.

   The patient grasped the electrodes, and took the shock to relieve all sorts of ills: paralysis, palsies, rheumatism, tumors, sprains, chilblains, inflammations, incontinence... Presumably the placebo effect caused a certain number of cures. For diseases of the lower extremities, an iron slipper was used as one electrode, and the second electrode applied to the knee.

Electricity (Medical Machines)

electric motor

Electric Motor

Its label 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.
 

Electric Motors (Modern)

newtons rings

Newton's Rings

Isaac Newton first discussed the colored interference fringes that we now call Newton's Rings in a communication to the Royal Society in December 1675, and presented an expanded account in his book "Optics" (1705). The original observation was first made with a wedge-shaped air-gap between the surfaces of two prisms, but later used the now-standard technique of pressing the convex surface of a lens against a flat glass plate. The familiar colored rings are best observed in monochromatic light.

Optics

planisphere

Movable Planispheres of the Heavens at Every Minute (missing)

Cardboard aids to astronomy students, were published by Henry Whitall, 512 Arch Street, Philadelphia, Pennsylvania in 1862. The sentence "To Astronomy what a Map is to a Geographer" is at the center of each instrument and the Greek alphabet, "as applied to the stars", is given for reference on the left-hand side of the stationary, overlying part of it. The revolving part has the stars (left-hand apparatus) or the constellations (right-hand apparatus).

   The description in the 1889 Queen catalogue is: "Whitall's Planisphere. Showing the stars and constellations visible at any hour in the evening, for every night of the year. The most simple and satisfactory map of the heavens for the use of students and others extant. On strong cardboard. 15 inches in diameter. ...$3.00" Queen also sold a version on glass for use in a projector. 

Astronomy

planisphere
achromatic prism

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 Paris, and are listed at 50 francs in the 1853 catalogue.

Optics

variable resistance

Variable Resistance or Decade Box

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).

front and back view

 

Electrical Measurements

variable resistance back view
revolving armature engine

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 current to the electromagnet is cut off until the next iron bar is in range. A commutator is used to complete and then break the current to the electromagnet. This Froment-type motor was probably made in the second half of the 19th century.

Electric Motors

 

revolving bell engine

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 revolutions. The gearing also acted to keep down the rotation speed of the engine.

Greenslade category: Daniel Davis Instruments

tangent galvanometer
 

Tangent Galvanometer

The tangent galvanometer 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 first set up on a level surface and the coil aligned with the magnetic north-south direction. A current to be measured is sent through the coil, creating a magnetic field that causes the galvanometer needle to deflect from its north-south alignment. The magnitude of the current is deduced from the angle of deflection of the needle and the known strength of the earth’s magnetic field. Made by Elliott of London.

Electrical Measurments

telegraph

 

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 pencil to make marks on a continuously-moving strip of paper. The first instrument was made in 1836, and improved after Morse contacted Joseph Henry.

The use of the relay to allow the signal to be retransmitted to increase the range was invented by Morse, Henry, Wheatstone and Siemens. The first long-distance line was constructed between Washington and Baltimore with the assistance of federal funds, and the first message sent May 24, 1844. Printing or recording receivers were originally used. This improved model, dating from the 1870s, used a clockwork mechanism to pull a long strip of paper past a sharp point which was pushed into the paper by the electromagnet. Early on, the operators learned to distinguish the long and short sounds as the electromagnet clicked in and out, and relied almost exclusively on the sound, writing down the letters of the message by hand. It was sold by James W. Queen of Philadelphia at a relatively hefty price of $50.00.

 

 

Electricity

leiden jar

Leyden Jar

The Leyden jar is the earliest form of the condenser or capacitor. The jar allowed the electric charge produced by an electrostatic machine (for instance) to be accumulated and stored for future use. The first jars were made independently in 1745 by Ewald Georg von Kleist in Germany and Pieter van Musschenbroek in Leiden, about 35 km southwest of Amsterdam

Static Electricity

010

Discharger  

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.

Static Electricity

voltmeter

Voltmeter (missing)

This is the face plate of a Deprez-Carpentier voltmeter in the collection of historical instruments at Washington and Lee University in Lexington, Virginia.The voltmeter had a coil made up of many turns of fine wire. When this coil was made of a few turns of heavy wire, the instrument was an ammeter. The voltmeters cost upwards of $32.00, depending on whether multiplier coils were included, and the ammeters cost upwards of $24.00, with the higher prices including shunts for higher current ranges. 

Electrical Measurements

wall galvanometer

 

Wall Galvanometer

This was the culmination of over a century of development of current-measuring instruments which relied on the interaction of currents with static magnetic fields. These instruments were mounted on a solid wall to prevent vibration, and a telescope and curved scale combination used to determine the deflection of the galvanometer. Because of its great sensitivity, you had to plan your measurements so that the coil did not burn out from putting currents of the order of tens of milliamperes through it.

 

Electrical Measurements

upright voltameter

 

Upright Voltameter (missing)

The Volt-Ammeter at the left has a movement and case by the L.E. Knott Apparatus Co. of Boston. 

However, it appears to have had some additions to turn it into a dual-use instrument. Presumably there is one terminal (probably negative) in common. One of the other terminals have a large multiplier resistance to convert the basic galvanometer into a voltmeter, while the third one leads to the basic movement and a shunting resistor to form the ammeter. The instrument has been hand-calibrated.

Note: image is from Fredonia. Our looks similar/identical?

Electrical Measurements

cenco wimshurst electrostatic machine

Cenco Wimshurst Electrostatic Machine

When the large center disk, made of non-conducting material with metallic strips attached, was turned using a hand crank, fixed metallic brushes rubbed against the metallic strips causing them to become charged. The charge was drawn off and collected in Leyden jars at lower left and right. Movable rods connected to the Leyden jars could be put to use in driving pieces of electrical demonstration equipment, like the Electric Whirl.

Static Electricity

001

Prism

A prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use "prism" usually refers to this type. Some types of optical prism are not in fact in the shape of geometric prisms. Prisms are typically made out of glass, but can be made from any material that is transparent to the wavelengths for which they are designed. A prism can be used to break light up into its constituent spectral colors (the colors of the rainbow). Prisms can also be used to reflect light, or to split light into components with different polarizations. These are made by Duboscq in Paris.

Optics

003

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 difficult to pull the spheres apart: a famous image shows teams of horses pulling in opposite directions unable to part the spheres. This device was designed by German scientist Otto von Guericke in 1650. Von Guericke was also the mayor of Magdeburg, thus the device name. This device is still used as a teaching tool to demonstrate the force of air pressure.

Pheumatics

006

Electric Whirl and Electric 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 pointed ends into the air. Also, a small conducting ball suspended by a thread begins to move alternately from contact with one of the bells to the other, picking up charge from one, and discharging it onto the other.

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008
Lens?

Circular Protractor

  Theodolite
  Planimeter
  Sextant
  Buoyancy of Air
  Phenakistoscope
  Analytical Balance
  Electrotome
  Kaleidoscope
  Glass Press
  Tachometer
   
   

 

For more information, or exhibit ideas, contact Yolanda Merrill at Leyburn Library.

 

 

 

 

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