Description and Notes:
The above picture shows the two sides of this boxwood slide rule. It is a proof slide rule which is used for calculating the percentage proof of alcohol. It also has thermometer scale engraved on the stater. This type of slide rules were often included in a deluxe set of Sikes's hydrometer.
This slide rule is dated to c1840 as according to Directory of British Scientific Instrument Makers 1550-1851, p. 171, the maker of this rule, J. Long, could be James Long (w 1781-1811) or Joseph Long I (w 1821-1846) or II (fl 1827-1833).
