A late 19th century mahogany cased Sikes' Hydrometer with Hydrometer tables book; and a brass and ebony slide Rule the Hydrometer with the maker's mark for T.O Blake, 58 Hatton garden, London, Serial no. 2184, circa 1880, used to determine the concentrated strength of spirits, housed within a fitted case with an ivory maker's plaque, opening to a brass hydrometer float, eight weights, a ruler and a thermometer, the weights and float bearing a stamped serial number, accompanied by the publication Sikes' tables of the Concentrated Strength of Spirits, the case 25 cm long; together with a brass mounted ebony slide rule, 38 cm long