Sikes Hydrometer by Husbands and Clarke, Bristol, England in its original mahogany box. 19th century. The Sikes Hydrometer was used to determine the alcohol content of spirits in determining its proof. This set includes a brass float, thermometer, and 10 weights used to measure the specific gravity of the liquid (labeled 10, 20, 30, 40, 50, 60, 70, 80, 90, plus the calibration cap weight). Each weight is stamped with a serial number that matches the one on the float, #15867 (the #20 weight is a replacement marked Loftus). Bartholomew Sikes invented the design in 1802, and, in 1816, the Board of Excise enacted the Sikes Hydrometer Act which made it the official legal instrument for determining the alcohol content of spirits. It remained the standard legal unit until 1907 and continued in popular use well into the 20th century. Size of box: 9.75 inches x 4.25 inches x 2.25 inches. Excellent antique condition, apart for one missing latch on the case. The thermometer has an ivory back plate, and the manufacturer's plaque on the case's cover is also ivory.