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Description: | PW 250V 40W (black stencil on the end cap). 1P5I ? (written in black on the base of the cane). MANU Unsigned. crca 1925 [England] DES after SWAN,Joseph,Wilson,Sir. 1878 Newcastle-Upon-Tyne England This is a 250 volt 40 Watt general lighting service lamp with a Swan double contact bayonet two pin cap type No B22/25x26 and a clear bell shaped envelope with a pip or pintel. The single ductile tungsten squirrel cage filament is clinched to the nickel lead in wires. The union between the copper and the nickel is made by a short length of copper sheathed nickel iron in the base of the cane. It is supported by a lower set of nine stout molybdenum wires and an upper set of ten mounted on a central glass cane. The support wires are in the form of fine crooks in the top set and heavier crooks in the bottom.The first tungsten filaments were developed circa 1906 using a process similar to the squirted carbon filament but a ductile tungsten process, by which tungsten powder is compressed and then forged into billet before being drawn through a series of diamond dies, was developed in 1909. The envelope is a hand blown vacuum type with a pintel or pip. The bulb being evacuated via the pintel in the top of the envelope. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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