| Reference number | MOB/038 |
| Level | Item |
| Title | Protractor by Jesse Ramsden |
| Date | 18th century |
| Description | Ten inch brass protractor, divided into 1/2 degrees and indented at 90°, 180°, 270° and 360° of the circular dial. Brass arms extend into the centre, dividing it into quadrants and a movable arm pivots from the centre, carrying a vernier, reading to one minute. This arm extends beyond the vernier, with a brass strip fastened to the top, a small hole visible at its end, which would have contained a sharp metal pin, to prick or mark angle points. A round hole is visible at the centre, where crosshairs would have been placed to mark the origin point for measuring angles. Engraved 'Ramsden London' and 'R.S. 61' across the immovable arms. |
| Extent | 1 instrument |
| Format | Scientific Instrument |
| Materials | Brass |
| Notes | On loan to the Science Museum, early 20th century- 2019 |
| Access status | Open |
| Provenance | Exact provenanc unknown. Possibly one of the instruments commission by General Roy for a Royal Society sponsored project: to determine the difference of longitude between the observatoires of Greenwich and Paris. The known of these objects include a 100 foot steel chain, six glass rodsand a theodolite. |
| URL description | Digital version available on The Royal Society Picture Library |
| URL | https://pictures.royalsociety.org/image-rs-18186 |
Fellows associated with this archive
| Code | Name | Dates |
| NA6963 | Ramsden; Jesse (1735 - 1800) | 1735 - 1800 |