[welz-bak, -bahk; Ger. vels-bahkh] 
| a brand of gaslight consisting essentially of a Bunsen burner on which an incombustible mantle (Welsbach mantle) composed of thoria and some ceria becomes brilliantly incandescent when exposed to flame. |
| Wels·bach burner (wělz'bāk', -bäk') A trademark used for a lamp consisting of a gas burner and a gauze mantle impregnated with cerium and thorium compounds that becomes incandescent when heated by the burner. |
bæk