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).
Catalog page with illustrations and descriptions of different types of sparks.
| Identifier | ExFiles\Box 63\4\ scan0020 | |
| Date | 26th May 1918 guessed | |
| (20) (97) ZR6/C/2000/2/A/A as for 600/2/A/A (98) ZR6/C/2000/2/A/B 3 short sharp sparks. (99) ZR6/C/2000/2/R/A striations. Very much as for 600/2/R/A but some ordinary bushy arc in evidence. (100) ZR6/C/2000/2/R/B Several sparks some straggly. (101) ZR6/C/2000/5/A/A Sharp sparks only. Some missing. (102) ZR6/C/2000/5/A/B One or two short sharpp sparks. | ||