sikes hydrometer london A Sikes hydrometer is a type of alcohol content tester that was developed by Bartholomew Sikes in the early 19th century. It was used by the British government for calculating the duty (tax) on spirits, and many were manufactured in London by various companies. Key facts about Sikes hydrometers and their London origins: Official standard: After winning a competition held by the Board of Excise, Bartholomew Sikes's design was mandated by an 1816 Act of Parliament as the official instrument for determining alcohol duties throughout the United Kingdom. Function: The instrument consists of a brass float with a graduated scale, a set of weights, a glass jar, and a thermometer. To use it, an excise officer would place the float and weights into a sample of spirits. The reading on the scale, combined with the liquid's temperature, would be used with special tables to calculate the alcohol proof. London manufacturers: Numerous London-based instrument makers produced these sets for the government and private distillers. Examples include: Robert Brettell Bate: Manufactured hydrometers for the Board of Excise and Customs. Dring & Fage: J. J. Hicks: A London-based company that created Sikes hydrometers, including versions for export to places like Australia.