Table of measurements and observations for different annular gaps, detailing spindle and hole diameters and the resulting coronal discharge.
| Identifier | WestWitteringFiles\M\2October1924-December1924\ Scan86 | |
| Date | 8th October 1924 | |
| - 32 - 8.10.24. X.4645. ANNULAR GAPS. | Gap particulars. | Spindle dia.(a) (mm.) | Spindle dia.(a) (inches) | Hole dia. (b) (mm.) | Hole dia. (b) (inches) | Gap (mm) b-a {Mr Adams} /2 | b/a | a {Mr Adams} /b | Remarks. | |---|---|---|---|---|---|---|---|---| | M.L. Gap originally. | 1.3 | .051 | 6.42 | .253 | 2.56 | 5.01 | 20 | Invisible but audible coronal discharge. | | Lucas gap originally. | 1.85 | .073 | 8.85 | .348 | 3.5 | 4.78 | 21 | Visible and audible coronal discharge. | | Lucas gap Our set A. {Mr Adams} (std). | 2.21 | .087 | 8.25 | .325 | 3.02 | 3.74 | 27 | Invisible but audible coronal discharge. | | Lucas gap Our set B. | 2.54 | .100 | 7.95 | .312 | 2.70 | 3.12 | 32 | Ditto. | | Lucas gap Our set C. | 3.17 | .125 | 7.95 | .312 | 2.39 | 2.50 | 40 | Very slight audible discharg | EPC. | ||
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).