Further Methods of Forecasting

In the wake of John Herschel and others' work, weather prediction increasingly became linked with the measurement of specific physical variables using scientific instruments. Throughout the late nineteenth and early twentieth centuries, a variety of pocket weather forecasters appeared to aid this work.

Pocket weather forecaster dial
Image 1 Wh.0895. A pocket weather forecaster dial by the British firm Negretti and Zambra, 1900-1939. Image © the Whipple Museum.
The Daily Weather Guide
Image 2 Wh.4564. 'The Daily Weather Guide', made 1900-1950. Image © the Whipple Museum.
Sunshine recorder
Image 3 Wh.5173. A Campball-Stokes sunshine recorder made by R. Fuess, 1920-1960. Image © the Whipple Museum.

Pocket weather forecasters

The scientific instrument firm Negretti and Zambra produced a weather forecaster intended to be used with a barometer and weather vein. Two dials were rotated according to barometric reading of air pressure and the direction of the wind (Image 1). The corresponding chart on the reverse indicated likely changes in weather for the next 12 hours.

In 1938, the firm D. & K. Bartlett produced a weather forecaster based on the type of cloud and the direction of the wind (Image 2). The central dial rotated to reveal a weather prediction.

Sunshine recorder

Theories of solar heat affecting the global atmosphere persisted throughout the nineteenth and twentieth centuries. The Campbell-Stokes sunshine recorder was invented in 1853 by John Francis Campbell (1821-1885) and later improved by George Gabriel Stokes (1819-1903) in order to measure the hours and intensity of sunshine (Image 3).

Campbell's original sunshine recorder consisted of a glass sphere positioned in a wooden bowl. The glass focused sunlight to a point that burned a pattern into the wooden bowl depending on the brightness of the Sun. The path of the Sun and the intensity of the light would be charred as a line. For instance, if the day was overcast, the burnt line would be very faint.

Stokes improved the instrument by devising a metal cradle for the glass, which held a strip of card behind the sphere that could be changed daily. The card was printed with a grid to better record the Sun's height above the horizon.

Allison Ksiazkiewicz

Allison Ksiazkiewicz, 'Further Methods of Forecasting', Explore Whipple Collections, Whipple Museum of the History of Science, University of Cambridge, [http://www.hps.cam.ac.uk/whipple/explore/meteorology/weatherforecasting/furthermethods/]

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