Accession No
1995
Brief Description
glass vacuum tube, 1875–1925
Origin
Maker
Class
physics
Earliest Date
1875
Latest Date
1925
Inscription Date
Material
glass; metal (white metal, brass)
Dimensions
length 260mm; breadth 90mm; height 205mm
Special Collection
Cavendish collection
Provenance
Transferred from the Cavendish Laboratory, University of Cambridge, in 1974.
Inscription
Description Notes
Colourless glass vacuum tube, two spherical bulbs joined by a short length of straight tubing, also joined by tubing which leaves reservoirs at right angles to straight tubing and forms a large spiral joining the reservoirs. Closed side arm from centre of spiral. Long anode and cathode probes almost meeting in the centre of the straight tube.
Condition good; complete.
References
Events
Description
Glass has been prized for centuries for its transparency and moldability. It’s these qualities that make it one of the most important materials in the history of physics. The Whipple cares for a large collection of glassware from the University of Cambridge’s Cavendish Laboratory of Experimental Physics.
Most of it dates from the 1880s to the 1930s, when Cavendish Professor J.J. Thomson and his students were studying the mysterious glows and rays that can be seen through the glass when electricity is run through a gas in a partial vacuum. These studies led to Thomson’s discovery that cathode rays were made up of sub-atomic negatively charged particles in 1897. He named them corpuscles: we know them as electrons.
The Laboratory’s technical team included gifted glassblowers. They created and repaired the intricate vessels to order: whatever the researcher needed for his or her experiments.
Many of the technicians joined the Laboratory as young boys and remained there throughout their careers. This meant there was an unbroken continuity of craft and technical knowledge across the Laboratory’s first six decades.
Scientific glassblowers work with prefabricated tubes of set diameters and thicknesses. They use a flame and their own breath to expand and bend them into the shapes needed for each experiment.
At the Cavendish Laboratory, all students were encouraged to learn glassblowing, but it was very difficult to master.
“Only those who have tried it know how exasperating glass-blowing can be, and how often when the apparatus is finished it breaks and the work has to be begun again.”
J.J. Thomson, Cavendish Professor, 1936
This intricate form was blown and shaped using standard glass tubing. It would take the craftsman about half a day using a pump to remove the air from one tube. It might then be filled with a specific (sometimes hazardous) gas, such as helium. It contains metal terminals to enable an electric current.
10/07/2025
Created by: Hannah Price on 10/07/2025
FM:44932
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