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C.T.R. Wilson Cloud Chamber


This instrument consists of a wooden base, to which various components are attached. The components on the instrument are mainly painted dark green.

The components on the base are: A toggle switch in a white ceramic base is located in one cornet, at the edge. This is next to a rounded electrical motor, sitting on a second wooden base that is attached to the base with four bolts. This motor is attached by an insulated yellow wire to a rheostat consisting of a cylindrical coil with a sliding section that rides along a metal bar along its length. This is next to two white round objects sitting low on the base. A second yellow wire passes through a hole in the wooden base.

At the other end of the base to the motor is a pump apparatus consisting of a belt driven wheel with a handle attached and other pieces, and a short, disc-shaped cylindrical glass chamber set in a metal surround that sits on a metal support structure with various adjustments via knobs and screws. These pieces are on their own metal base and all are painted green. This metal base is bolted to the larger wooden base.

A second switch made of copper with a black handle set on a wooden base is affixed to the wood next to the chamber and pump assembly.

Accession Number:

Alternative Name:

Cloud Chamber, Expansion Cloud Chamber, Wilson Condensation Chamber

Primary Materials:

Glass, Metal: Copper Alloy, Metal: Iron Alloy, Plastic, Wood, Leather (Belt)


Old inventory number = “Phy 12”

A metal label affixed to the wooden base reads: “THE CAMBRIDGE AND PAUL INSTRUMENT CO. LTD. LONDON AND CAMBRIDGE” with a serial number stamped below this: “016436”.

A metal label on the motor reads: “BODINE ELECTRIC CO. CHICAGO, U.S.A.” “DIRECT CURRENT” “No. 34454 H.P. 1/8 WIN. DING SHUNT VOLTS 110 R.P.M. 1800 AMP. 1.4 TYPE D 1/80 DUTY TEMP. _

The pump and chamber assembly has a metal label affixed to its base reading: “C12666”, “THE CAMBRIDGE AND PAUL INSTRUMENT CO. LTD. LONDON CAMBRIDGE”. The number “650” is etched on the wood below the Cambridge and Paul label.

The rheostat has a label reading “Zenith” and “1.2 Amps, Ohms 177” and one reading “MOTOR”.
In white lettering on the copper switch: “No. 9.24”

Dimensions (cm): Height = 24, Width = 30, Length = 86.5


A cloud chamber is a particle detector used to make visible particles ionizing radiation. These particles cause distinctive ‘tracks’ to appear through water or alcohol vapour formed in the glass chamber when the chamber is under low pressure and the gas inside has expanded and cooled.


Good: The wooden base of the instrument is marked and chipped in places. There are some open holes that may indicate removed parts.

The metal components are in good condition, with signs of use in the form of wear marks on the wheels driving the pump, and scratches across the surface of the pump, the metal base and the metal surround of the glass chamber. The glass chamber is intact although dirty. The leather belt. One belt may be missing as the large wheel with a handle has a notch in it where a belt might run.

Associated Instruments:

Manufacturer: Cambridge & Paul, Cambridge

Date of Manufacture: c. 1919-1924


Additional Information and References:

Historical Notes: