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).
Comparison of different types of electrical spark and arc characteristics with corresponding sketches.
| Identifier | ExFiles\Box 63\4\ scan0031 | |
| Date | 31th May 1933 guessed | |
| D/2000/2/A Thick and thin spark. Bushy arc. Occ. thin sparks anywhere Occ. striations. D/2000/2/B As sketches. D/2000/5/A Same as for D/2000/2/A only less. D/2000/5/B Single spark and arc. D/2000/7/A Same, but still less arc and more striations. D/2000/7/B Single spark. | ||