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).
Diagrams illustrating the characteristics of electrical sparks and arcs under different conditions.
| Identifier | ExFiles\Box 63\4\ scan0012 | |
| Date | 26th May 1918 guessed | |
| (12) (49) ZA2/600/2/N/A Sparks & Arc. (50) ZA2/600/2/A/B Sparks & Arc. (51) ZA2/600/2/R/A Same as for advance but very slightly less arc. (52) ZA2/600/2/R/B Sparks & Arc. (53) ZA2/600/B/A/A Single spark and arc. (54) ZA2/600/5/A/B Single spark and some arc. Some dots of light. | ||