ELECTRIC LAMPS

Hawera Star, Volume XLV, 11 January 1926, Page 8

ELECTRIC LAMPS

MAHVKLS OK IXUENIMTV. PRIEiS'BiST- DAY PROCESSJvS. Eew people when glancing . a t- ie übiquitous electric lamp realise the wealth oi ingenuity expended in its nmnul'acture. or know the romance o-l its history (writes K. C. Pndlipp, iu the Sydney Morning Herald). let the story ol' its evolution from the carbon filament lamp of Edison m America, and Swann in England—both working independently —to the gas-filled lamp of to-day, is one ol absorbing interest, not only to the engineer, but to all who are- fortunate to

use them. inside the glass hull) can be seen the fine fiilament which glows at white heat when an electric current is passed through it, and in this connection it is interesting to note that the thickness of the filament is an indication of the candle power of the lamp. Jn lamps of low candle-power it is made of extremely fine wire that can be seen through the glass bulb only with difficulty, w-lierea«s in liigher caiidlc-lamp.s the filament! is appreciably thicker. Jn the earlier days it was made of carbon, and the difficulty was to secure this protean element in the form of a tough fibre, so Edison scoured the botanical world for a suitable substance, finally selecting bamboo. Indepedently, Swann rather cleverlv built up his filament by dissolving cotton wool in zinc chloride .and squirting the resulting treacley glass through a fine syringe into alcohol, after which it i« washed, dried, mid wound into- formers of the req u i reel si 1 a pe , wli i ch. we re "t lie n b alee d in a furnace so that everything else was driven off except the carbon. Thus Swann changed cotton wool into tough threads of pure carbon.