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Cathode Ray Tube with Coral


A cathode ray tube with a long bulb containing fluorescing coral, mounted on a turned wooden base. The long narrow bottom part becomes pear-shaped after 14 cm, coming to a point with a metal, disc-shaped electrode on the top. Halfway up the narrow glass part is a short, 4 cm projection with another electrode. Three coral-like stones are mounted inside the bulb on glass mounting arms.

FROM OLD CATALOG CARD: “elongated 36 cm glass bulb on turned wooden base; 3 pieces white coral-like substances supported in centre of bulb by 20 cm glass tube; disc shaped electrode at top of bulb; electrode held in projection from stem”

Accession Number:

Alternative Name: Crookes Tube with coral

Primary Materials: Wood, Metal, Glass

Markings: Old inventory number = phy72.

Dimensions (cm):

Height = 46, Base Diameter = 10, Bulb Diameter = 12


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: