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Special Exhibition Label: 'Atmospheres: Investigating the Weather from Aristotle to Ozone' (19/10/2012 - 07/04/2013)

Hygrometers for Humidity

Hygrometers measure the moisture content of the air. Several different principles of operation have been adopted.

Above is a hair hygrometer of about 1840, by the well-known London firm of Watkins and Hill. The reading indicated on the dial is created by an animal or human hair under tension, whose length changes with humidity.

On the left is a wet and dry bulb hygrometer by G. H. Zeal, London, c.1930 (see other examples in the case on the left). Designed to be mounted on the wall its central barrel is a cylindrical table of relative humidity values.

[Inv 58334 & 44192]

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