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Cathode Ray Tube with Two Minerals


A pair of 12 cm glass bulbs are mounted on a turned wooden base. The bulbs are joined by a T-shaped glass tube that runs from the base to the bottom of each large bulb. Inside each bulb is a glass support or arm holding a mineral with small glass fingers.

FROM OLD CATALOGUE CARD: “2 12 cm glass spheres held by T-shaped glass tube; support in turned wood base; each contains white substance supported in centre by glass tube; disc shaped electrode in top of each; overall height 32 cm.”

Accession Number:

Alternative Name: Crookes tube with two minerals

Primary Materials: Wood, Glass, Metal

Markings: Old inventory number = phy74.

Dimensions (cm):

Height = 32, Width = 24.5; Bulb: Diameter = 12; Base: Diameter = 12


Minerals fluoresce 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: