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).
Classification chart illustrating and describing different types of electrical sparks and arcs.
| Identifier | ExFiles\Box 63\4\ scan0030 | |
| Date | 17th July 1917 guessed | |
| D/600/2/A Single spark and bushy arc some striations Thin outer spark sometimes D/600/2/B Sparks and some arc. D/601/2/A Same as D/600/2/A but shorter arc and only occl. outer spark. D/601/2/B Single spark Slight arc. D/600/1/A Occl. single sparks and sometimes striations. D/600/1/B Occl. single spark. | ||