The science and practice of photography : an elementary textbook on the scientific theory and a laboratory manual (1920)
Roebuck, John R. (John Ransom), 1876-1965 · New York ; London : D. Appleton and company · leaf 311
APPENDIX 281 eral arrangement. On these ways are carried two lamps and between them the box with the photom- eter comparison head. They are held in line by a slotted piece of brass tube sliding on the inch> … Fig. 52. Central Box of Bench Photometer. guide. The most satisfactory lamps available are the nitrogen-filled concentrated tungsten filament locomotive-headlight incandescent lamps, and the 100 watt size will give light enough to read all the ordinary densities. They usually run on lower volt- age…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
![An illustration from [Volume I.]](https://img.insideoutlibrary.com/img/200/erara-31314765-470-1.webp)
![An illustration from [Graphophone patents] (1878)](https://img.insideoutlibrary.com/img/200/ia-graphophonepaten02unit-132-51.webp)
