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).
Illustrated log page detailing various spark test results with corresponding observations.
| Identifier | ExFiles\Box 63\4\ scan0019 | |
| Date | 26th May 1918 guessed | |
| (19) (91) ZR6/C/600/5/R/A Three or four sparks sometimes followed by pseudo arc as illustrated under 2/R/A (92) ZR6/C/600/5/R/B Single sparks (93) ZR6/C/600/7/A/A No spark (94) ZR6/C/600/7/A/B No spark. (95) ZR6/C/600/7/R/A No spark (96) ZR6/C/600/7/R/B No spark. | ||