Emissivity of straight and helical filaments of tungsten
A 1918 National Bureau of Standards technical paper on the emissivity of straight and coiled tungsten lamp filaments, written for physicists and lighting engineers. The plates are line figures: plotted curves with hand-marked data points and specimen numbers, hatched cylinder diagrams tracing light paths between coil turns, and lettered arrow schematics useful as spare scientific ornament or diagram vocabulary.
