| RefNo | MS/119/2/60 |
| Level | Item |
| Title | Letter from Humphrey Lloyd, Killiney, Dublin to Charles James Buchanan Riddell |
| Date | 20 July 1845 |
| Description | Lloyd does not see an advantage to increasing the firmness of the division of the reflected scale.
Lloyd discusses the optical power of large instruments and its capabilities. The limit of the optical power is distinguishing one tenth of a minute. Lloyd informs Riddell that the limit should read to the same degree of precision, but this can only be done with a large expansion circle. Lloyd recommends an eight inch circle divided to 12 inches.
Lloyd suggests adopting decimals of a minute as far as possible in all magnetic readings.
Discussion on the collimator magnet. Lloyd is waiting to receive [James Clark] Ross’s small magnets which he is fitting with new lenses. It would be advantageous to make the instrument available for the determination of the absolute meridian.
Discussion on the induction inclinometer, and what it should include. |
| Extent | 8p |
| Format | Manuscript |
| PhysicalDescription | Ink on paper |
| AccessStatus | Open |
Fellows associated with this archive
| Code | PersonName | Dates |
| NA8252 | Lloyd; Humphrey (1800 - 1881) | 1800 - 1881 |
| NA7327 | Riddell; Charles James Buchanan (1817 - 1903) | 1817 - 1903 |