This lamp is to serve as a source of radiation from the visible into the far infrared. The heating unit consists of sheets of ashed Welsbach mantle heated by the glow or arc discharge formed between terminals connected to the secondary of a high potential transformer. When operated in air, a small, pointed gas flame is allowed to play on the mantle, thus steadying the electrical discharge and increasing the temperature. From 0.7 to 15µ, gas plus electricity are used, whereas, from 15µ to 150µ gas alone is employed. When the lamp is operated in a partial vacuum, variations in spectral distribution are effected largely by working at different pressures. At pressures around 10 cm the emission is similar to that of the gas Welsbach in the region of longer wave-lengths, while at pressures near 30 cm the emission rivals that of a Nernst lamp in the near infrared (0.7 to 15µ).
A. H. PFUND, "The Electric Welsbach Lamp," J. Opt. Soc. Am. 26, 439-441 (1936)