From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Note on how candle power varies for metal and carbon filament lamp bulbs based on terminal P.D.
| Identifier | ExFiles\Box 166\4\ img101 | |
| Date | 2nd February 1931 | |
| X6089 2.2.31. X.6089. METAL FILAMENT LAMP BULBS. The candle power of metal filament lamp bulbs varies approximately as the 4½th power of the terminal P.D. N.B. In the case of carbon filament lamps this is the 5½ power. EFC. | ||