With a sketch comparing a parallel tube and a bulged tube.
| Identifier | ExFiles\Box 15\1\ Scan387 | |
| Date | 25th September 1930 | |
| Parallel □ Tube E81385- Bulged □ " E81389. 16 / L62 ROLLS-ROYCE, LIMITED PRINT ROOM, 25 SEP 1930 | ||
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).