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Cathode Ray Tube with Coral


A large pear shaped glass bulb is attached vertically to a turned wooden base. There is a tall glass arm or stand inside of the bulb which holds a pink mineral, likely coral. Near the bottom of the bulb, a perpendicular glass tube containing an electrode projects outward. At the top of the inside of the main glass bulb is another electrode with a metal disk attached via a short metal rod.

Accession Number: 2009.Ph.245

Alternative Name: Crookes Tube with coral

Primary Materials: Wood, Metal, Glass

Markings: Old inventory number = phy26.

Dimensions (cm): Height = 51 cm, Diameter = 12.5 cm


Coral fluoresces under bombardment of cathode rays. Possibly used for spectroscopy.


Associated Instruments:


Date of Manufacture:


Additional Information and References:

In October 1898, instructor and future professor J.C. McLennan visited the Geissler Establishment, in Bonn, Germany. The Geisslers were famous for the manufacture of Crookes Tubes. McLennan reported in a letter back to Professor James Loudon that he had purchased some of these for the Toronto physics laboratory, including at least one with a “phosphorescent mineral”, which, he reported, “gives the most beautiful effect that I have seen.” (McLennan, 1898)

There are numerous examples of phosphorescent mineral tubes in the collection. It is possible that one, or more, of these were purchased by McLennan during his 1898 trip to Bonn.

Letter from J.C. McLennan to J. Loudon, October 10, 1898. University of Toronto Archives B1972-0031 Box 004 File 43

Historical Notes: