Maker

Casella, London

Model

Whirling Psychrometer

Serial Number

nil

Dimensions

220 x 144 x 28 mm (including handle)

Image

Description

This whirling posuchrometer has a rectangular wooden body (182 x 52 x 12 mm) with two recesses for two mercury-in-glass thermometers. The thermometers are about 145 mm long, have a range from -20°C to +50°C and are graduated in one-degree intervals (numbered every 10 degrees). One of the thermometers carries a gauze wick around the bulb.

The device features a handle with bearing at one end and a small storage space at the other. The temperatures can be estimated to 0.1°C. When in use, the wick has to be wettened with distilled water and the body with the thermometers whirled around the handle. The difference between dry and wet bulb temperatures can be used to compute the partial water wapour pressure (and relative humidity) of air.

History & comments

Most likely used by the School with early EDM instruments such as Tellurometers and Geodimeters. (See items 406, 407, 411, 412)

Conservation

no box or container

Condition

some blemishes in the varnish

Remarks

Marked P/C 11958

Dates

Catalogued by JMR in Sep 2011. Photo by JMR.