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Helixon Stand
In a listing of physics equipment from around 1900, this device is called a "Helixon Stand." The term "helix" was used to describe a coil of wire through which an electrical current could be passed in order to magnetize a piece of steel passing through the coil. This appears to be such a helix, and perhaps Helixon was a trade name.
Lamp with Scale
Before electric lights were available, oil lamps such as this one were used for illumination in the laboratory. The motion of the mirror on the movable part of a galvanometer was observed either by looking with a telescope at a scale reflected in the mirror or by observing the movement of a spot of light reflected from the mirror onto a scale. This lamp and scale were used for that purpose--light from the lamp passed through a narrow slit to the mirror, and then it was reflected back onto the scale.
Post Office Bridge
This is a Wheatstone bridge designed to locate a short circuit in a telephone or telegraph line by measuring the resistance to the short. It gets the name "post office bridge" from its adoption by the British Post Office, which operated telegraph and telephone systems in addition to delivering mail. The upper row of plugs determine a ratio and the lower rows are a standard resistance.
Hand-Driven Generator
This hand-driven generator was made by Palmer & Hall of Boston. Turning the wheel rotates two coils wound about iron cores which are at the ends of a horseshoe permanent magnet.
Standard Resistor with Mercury Cups
This resistor is exactly 10 ohms at a temperature of 23.7 degrees C. It was purchased in 1892 for $5.00.
Connection to a circuit was made through mercury in the cups into which the heavy leads from the resistor dip.
Astatic Galvanometer with Glass Dome
A galvanometer is a device for detecting electric current. The galvanometer pointer deflection is from electric current passing through a coil immersed in a magnetic field from permanent magnets.
Galvanometer with Three Horseshoe Magnets
These two galvanometers each have three horseshoe magnets. The coil beside each magnet should be suspended vertically between the poles of the magnets.
