Robert Bate's hydrometer Pevensey wearing a hat with a

wearing a hat with a bow

The River Lea and Stratford Bridge with a covered cart crossing

The material they got on why the Needle was discovered was put in a 30 minute radio show

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

Robert Bate's hydrometer Pevensey wearing a hat with aA 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