This Sike’s Hydrometer was donated by the Port Fairy Customs Office as it was no longer required by them due to a change in the law. The hydrometer was part of a system for Ullaging or calculating the amount of liquid remaining in a container of liquor such as a barrel, and the amount of alcoholic content in the contents. It can also measure the free space or head space remaining. Hydrometers were used to measure the density, or relative density, of liquids from the late 1600s. In 1816 Bartholomew Sikes won the competition for the most useful accurate hydrometer. Hydrometers were commonly used by distillers, vintners, and brewers to establish accurate measures of alcohol concentration in their beverages. Following this manufacturing process, government inspectors and excise officers used them to check that the labelled indications of alcohol-proof were correct and that the right amounts of duty were being paid.The Sikes hydrometer is of local significance because of its association with the Government's Customs Office in Port Fairy, in the southwest region of Victoria. It is also associated with Bartholomew Sikes, whose design of a hydrometer was chosen in 1816 as being the most useful and accurate hydrometer. The hydrometer has evolved into the digital version available today to measure density of liquids.Sikes Hydrometer and thermometer in a fitted wooden case with crimson lining inside the lid and dark lining in the base. The case has ten vertical pegs to secure the weights. The brass hydrometer has a spherical float and eight thick brass horseshoe-shaped weights. The serial number is on each section of the float and all weights. Both sides of the float’s upper flat stem have a scale from 0-10, with five divisions between each number. The eight weights are numbered from 20 – 90 in increments of 10. The set includes a mercury thermometer mounted on an ivory back plate labelled with Fahrenheit and Centigrade Scales. The Sikes hydrometer set was made by Loftus of London. The hydrometer model is IID 510, Serial Number is 14674, calibrated by Longs, London. All parts of the float and eight weights are inscribed with Serial Number “14674” The float stem is stamped "SIKE'S IID 51o” Calibrator, "LONG LITTLE TOWER ST LONDON" The weights are numbered individually ”20”, “30”, “40”, “50”, “60”, “70”, “80” or “90” Each weight in inscribed; symbol “(J L) [inside an ova, with textured background]” The thermometer inscribed: “LOFTUS OF LONDON”flagstaff hill, warrnambool, shipwrecked coast, flagstaff hill maritime museum, maritime museum, shipwreck coast, flagstaff hill maritime village, great ocean road, measuring instruments, customs tax, weighing instrument, sike’s hydrometer, calibrator long of london, loftus of london instrument maker, loftus, j long, sikes hydrometer, scientific instrument, pressure measurement, measuring instrument, ullage tool, customs, excise duty, tax, alcohol content, proof, calibrate, standard weights and measures, tariff, scientific instrument makers, specific gravity, liquid density, alcohol testing, technology, alcohol measurement, proof spirit, wine and spirits merchants, local business, brass measuring instrument, port fairy, customs office, port fairy customs, joseph long, instrument maker