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).
Comparative study of different spark characteristics with diagrams and notes.
| Identifier | ExFiles\Box 63\4\ scan0029 | |
| Date | 17th July 1917 guessed | |
| D/200/2/A Single or two sparks (thick & thin) slightly bushy are somewhat striated. Thin outer spark. D/200/2/B Few small sparks. No arc. D/200/5/A Single spark sometimes. A few striations. Not very bushy arc. D/200/5/B Single spark sometimes. D/200/7/A No spark. D/200/7/B No spark! | ||