A new photo-electric cell is described which is composed of thallium, oxygen and sulphur. This cell shows maximum sensitiveness to light of wave-length about 10000 Angstrom units. Some of the best cells lower their dark resistance by fifty per cent. in.06 foot candles when the light source is a tungsten filament. The dark resistance of different cells may be from 5 megohms to 500 megohms. The induction and deduction periods of the cells are very small. The chief characteristics of the cell are mentioned.

DOI:https://doi.org/10.1103/PhysRev.15.289