| Clue | Source | Date |
|---|---|---|
| & 20: One finds resistance better when a dog is barking | ||
| <b>& 20</b>: One finds resistance better when a dog is barking | The Times Sunday Cryptic | 26 Jan 2025 |
| Charles -, 19th-century inventor of the English concertina and the Playfair cipher | Mirror Quiz | 30 Jan 2024 |
| Charles --, English scientist and inventor (1802-75) | The Telegraph General Knowledge | 04 May 2020 |
| Sir Charles ____ did not invent the bridge named after him | The Times Specialist Sunday | 10 Dec 2017 |
| English physicist-inventor: 1802-75 |