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Pointolite Bulb

Unidentified · Physics

A spherical bulb with a cylindrical screw end. The bulb has a pointed tip. The interior apparatus of the bulb consists of two vertical metal posts supporting a horizontal crosspiece that ends in a coil of wire. Beneath this on its own vertical support, and not quite touching the horizontal, is a shiny metal ball about 1.5mm in diameter.

This is a bulb for a Ediswan Point-o-lite lamp.

Accession Number:

Alternative Name: Point-o-lite Bulb

Primary Materials: Glass, Metal: Copper Alloy


Printed on the glass: “ROYAL EDISWAN POINTOLITE (PATENT).100CP”.

Dimensions (cm): Height = 12.5, Diameter = 8.5


This bulb is to be operated with a specialised “Pointolite” lamp. It is designed to emit a very bright point of light for use in experiments.


Excellent: The bulb is intact. It is not clear if the bulb is operational but no significant interior damage is visible. The horizontal crosspiece is darker at one end, suggesting heating or burning out. However, it is connected. The brass-coloured bass is oxidized and marked.

Associated Instruments:

Manufacturer: Royal Ediswan Pointolite

Date of Manufacture: 1920s-1940s


Department of Physics, University of Toronto

Additional Information and References:

There are a number of examples of Pointolite lamps in the collection, under 2009,ph.24, or

Historical Notes: