Signedon side edge of upper hydrometer stem: BUSS 33 HATTON GARDEN LONDON
on thermometer: BUSS LONDON
on bone plate inset on case lid: SIKES'S HYDROMETER / BUSS / 33 Hatton Garden / LONDON
on edge of slide rule: FARROW & JACKSON MAKERS LONDON
Inscribedon hydrometer: No. 42131 SIKES
FunctionThis was the legally required hydrometer for testing liquor proof strength in mid-19th century Britain.
A sample of liquor would be poured into the glass vase and its temperature measured with the provided thermometer. Then the hydrometer would be made to float in the sample, if necessary attaching a weight, for the water surface to mark a point on the scale.
The hydrometer is very precise with a total range from 0 to 100, a measurement determined by adding the weight attached to the bottom of the hydrometer to the number marked by the liquor's surface on the stem's scale.
Once the number had been determined, it would be used, together with the temperature, to find the proof strength using the slide rule or a published book of tables. (see references). More information on this instrument and its use is found on the following website.
Primary SourcesSikes' Tables of the Concentrated Strength of Spirits with Directions for the Use of his Hydrometer / established throughout the United Kingdom for estimating the duties on spirituous liquors by act of parliament 58, Geo.III, cap. 28 / to which is added TABLES OF SPECIFIC GRAVITY / adapted to the use of the hydrometer. [no editorial data in book].