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).
Hand-drawn and annotated diagram showing observations of sparks and electrical arcing under six different conditions.
| Identifier | ExFiles\Box 63\4\ scan0004 | |
| Date | 26th May 1918 guessed | |
| 4. (1) ZR6/150/2/A/A 3 small sparks striations arc. (2) ZR6/150/2/A/B Several small sparks. Very little arc effect. (3) ZR6/150/2/R/A Less arc than for advanced position above. Sometimes no arc, but only little sparks. (4) ZR6/150/2/R/D One or two little sparks. Little arc. (5) ZR6/150/5/A/A Single spark no arc. At decreased gap (4mm.) arc appears. Then spark here sometimes (6) ZR6/150/5/A/B One spark or two sparks no arc. | ||