Robert Bate's hydrometer Pevensey Three quarter length studio portrait

Three quarter length studio portrait of Peter William Barlow seated with his right hand resting upon a table

On each side are images of the Trajan and Naval Columns

bottom right The Middlesex Petition

England in 1842

The River Lea and Stratford Bridge with a covered cart crossing

Robert Bate's hydrometer Pevensey Three quarter length studio portraitA hydrometer with hinged wooden case manufactured by Robert Bate. Hydrometers are used to measure the density of liquids. The weighted end is placed into a liquid and the hydrometer sinks to a certain level. The specific gravity can then be read from the liquid level on the vertical scale. ca. 1836