Description
This discharge tube, with its fancy glass target, was made in the Cavendish Laboratory of Experimental Physics. It glows when connected to an electric current. A blue ray runs from the cathode (negative electrode) and creates a green glow when it strikes the glass in the area around the anode (positive electrode). The cathode ray creates a striking effect on a target like this glass bead, which lights up in the glow. To make a tube like this, the glass-blower needs to think inside-out.

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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 Cavendish 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.


10/07/2025
Created by: Hannah Price on 10/07/2025

Description
Discharge tubes contain one or a combination of the following: rarefied (thinned) gasses such as neon or argon, conductive liquids or minerals. When an electrical charge is passed through the tube different effects are created.