|
Date: |
|
Description: | Included in Observatory equipment of 1823 Marischal College Natural Philosophy Inventory (King's Archives). 'Value: one guinea', ' Standard foot Examined by Maskelyne ' on paper in Copland's hand sellotaped onto lid. See John S. Reid ' A new Look at Old Linear Measures ' Annals of Science, 46 (1989)
"This rule appears in our 1823 inventory valued at 1 guinea. A paper note in the hand of Professor Patrick Copland, probably written in the last quarter of the 18th century, flags it as a 'standard foot examined by Maskelyne'. Several pieces of circumstantial evidence point to this scale being a production of Jeremiah Sisson. We don't know what Maskelyne's examination was but the rule was re-examined in the late 1980s by John S. Reid and compared for accuracy and systematic error against a modern laser interferometric standard. The markings are extra-ordinarily accurate and free from systematic error. A faint line of guide dots was made by Sisson before marking off the clearly visible divisions. The random positional error in this line of dots is only 6.8 microns, which must be close to the limit achievable by hand division. The length of an inch derived from the position of the dots is 25.4036 0.0002 mm. The analysis of this rule (and others) can be found in a New Look at Old Linear Measures by John S. Reid in Annals of Science, pp 221 - 248, vol. 46 (1989)."
Author: Reid, John.S Date: 2003 | License: | http://www.abdn.ac.uk/historic/Copyright_terms_conditions.shtml | Publisher: | ABDNP University of Aberdeen, Natural Philosophy Collection of Historical Scientific Instruments | Rights holder: | 47718 | Temporal: | 1760-1785 | Source: | University of Aberdeen | Creator: | signed J. Sisson London ' Standard foot Examined by Maskelyne ' on paper in Copland's hand sellotaped onto lid ' | Identifier: | http://calms.abdn.ac.uk/Geology/dserve.e... | Go to resource |
|
|