Electric Egg

Electric Egg #10094
This electric discharge tube gets its name from its shape. A high voltage connected to the top terminal produces an electrical discharge from the inner electrode that changes in character as the air is pumped out of the "egg."
References: Max Kohl Catalogue No. 100 (c.1927) p.844; Gerard L’E Turner, Nineteenth Century Scientific Instruments, Berkeley, 1983, p.194.

Geissler and Crookes Tubes

Geissler and Crookes Tubes #10576, 10573, 10568
Heinrich Geissler (1814-1879) was a German inventor who devised a way to pump out a vessel to a higher vacuum than had ever been attained at the time. His sealed, evacuated glass tubes came to be known as Geissler tubes. An electrical discharge through a partially evacuated tube glows with a color depending on the type of glass in the tube and the gas inside. Studies of discharges in such tubes later led to the development of atomic physics.
Sir William Crookes (1832-1919) improved on Geissler's method of evacuating vessels and by 1875 achieved vacuums of about 1/100 mm of mercury. An electrical discharge through the highly rarified air in his tubes showed the existence of cathode rays culminating in the discovery of the electron. Roentgen was using a Crookes tube when he discovered x-rays in 1895.
References: Gerard L’E Turner, Nineteenth Century Scientific Instruments, Berkeley, 1983, pp.194-96; Otto Pressler, Elektrische Vakuum-Röhren, Leipzig, 1914; Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, pp.279-81.

Geissler Tube Rotator

Geissler Tube Rotator #10538
A pair of Geissler tubes is connected to the arms of this rotator. While connected to a high voltage, which causes a discharge in the tubes, the arms are rotated, producing a spectacular display, especially in a darkened room.
Reference: Otto Pressler, Elektrische Vakuum-Röhren, Leipzig, 1914, p.10.

Coolidge 4UD X-ray Tube and Shield

Coolidge 4UD X-ray Tube and Shield #10089
General Electric X-Ray Corp.
Electrons from a hot filament are accelerated by several thousand volts to a metal target where the impacts produce x-rays. The heavy outer shield is made of lead glass, which absorbs x-rays going in unwanted directions. This form of x-ray tube, devised by the American physicist William David Coolidge, led to the widespread use of x-rays in industry and medicine.
Reference: Central Scientific Co. Catalog F (1923) p.194.

X-ray Milli-ammeter

X-ray Milli-ammeter #10407
The depth of penetration of x-rays depends on the potential applied to the x-ray tube while the dosage (or film darkening) depends on the current to the tube and the time of exposure. X-ray machines used for diagnosis or treatment therefore need to have voltmeters and milliammeters for proper adjustment.

Luminous Tubes

Luminous Tubes #10445, 10481
Spirals of foil pieces inside the tube provide a conducting path for a high voltage discharge. Sparks between the pieces of foil produce a beautiful display in a darkened room.
Reference: James W. Queen Physical Instruments Catalogue, 1888, p.91-92.