Two rather lovely looking instruments that used to be used by The Board of Excise for calculating alcoholic strength and quantity in cask of barrel.
The purpose of a hydrometer is to determine the specific gravity of a liquid. From this it is often possible to determine the composition or strength of the liquid. The Sikes hydrometer was, for very many years, the standard means of determining the alcohol content of spirits and hence the duty payable.
In 1802 the Board of Excise held a competition to find a better instrument than Clarke’s hydrometer for revenue purposes and nineteen instruments were submitted for consideration. The winning design was that of Bartholomew Sikes, an employee of the Excise Commissioners. Sikes hydrometer was enshrined in legislation in 1816 with the Sikes Hydrometer Act and remained the legal standard until 1907.
Alcohol rules were used for calculating the quantity in a cask and/or the excise duty payable.
Farmar’s Rule, The Standard Slide Rule for the Entire Wine & Spirit Trade (Desk Size). Farmar held a number of patents for alcohol slide rules. This carried out a comprehensive range of functions including reducing, gauging, and calculating profit on sales.