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Object Overview
Before us is a Pocket Weather Foreteller produced by the famous London company Negretti & Zambra, dating to approximately 1925 and manufactured under Patent No. 6276 of 1915. The instrument survives together with its original printed instruction leaflet, as well as the original cardboard box embossed in imitation crocodile skin — a characteristic inexpensive yet visually attractive form of packaging used by the company for the mass-produced versions of its forecasting devices. Despite the comparatively modest material of construction, this is neither a toy nor a promotional novelty, but a genuine mechanical weather calculator developed from many years of observation of the relationship between atmospheric pressure, wind direction, and subsequent weather changes.
Structurally, the instrument consists of a system of three superimposed discs of differing diameters, two of which are movable and rotate relative to the base. All components are made of thin celluloid — one of the earliest industrial plastic materials of the early twentieth century. The intermediate disc remains transparent, whereas the upper and lower discs contain additives that render the material opaque and milky-white in appearance, imitating ivory. Such imitation ivory finishes were extremely popular in British scientific instruments of the interwar period, allowing an object to acquire a more expensive and “classical” appearance at substantially lower manufacturing cost.
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cardboard, celluloid, paper
The base of the instrument forms a large stationary disc. Around its outer edge is a wind-direction scale marked with cardinal and intermediate points, while directly beneath it is a barometric scale in inches of mercury corrected to sea level. Superimposed upon this scale is the transparent intermediate disc fitted with a small pointer marked “Set Wind”; this component is used to align the wind direction with the outer scale.
The upper central disc contains three small windows marked with the barometric tendencies “Rising”, “Steady”, and “Falling”. Through these apertures appear letters of the alphabet located on the lower disc, corresponding to twenty-six different weather forecasts listed on the reverse side of the foreteller. This disc simultaneously serves for setting the current atmospheric pressure as read from a barometer and for obtaining the resulting forecast letter. Once the appropriate letter has been obtained, the user reverses the instrument and consults the corresponding forecast printed on the back.
The operating instructions for the instrument were as follows:
The letters “S” (summer) and “W” (winter) indicated the season of the year: the former referred to the period from April to September inclusive, and the latter from October to March inclusive. The forecast was intended for the following twelve hours, and the optimal time for taking a reading was considered to be 9 a.m.
In fact, Negretti & Zambra produced several different versions of their weather forecasters. The earliest was a large brass table forecaster employing a concentric ring system of scales and predictions. This was later followed by a considerably cheaper and more commercially successful pocket version in celluloid with imitation ivory finish, produced from the 1920s onward. Finally, there also existed a more unusual table forecaster housed in a cast metal body finished in black enamel, fitted with a silvered metal dial, black lettering, and forecasts printed on paper wound around an internal roller mechanism.
The development of the system did not end there. The company began integrating its forecasting mechanisms directly into aneroid barometers — both pocket models, which are encountered comparatively frequently, and wall-mounted instruments, which today survive as exceptionally rare and visually striking collector’s pieces. In addition, Negretti & Zambra marketed complete forecasting sets combining a barometer with a foreteller. Small watch-size barometers were typically paired with the celluloid versions of the forecasting device, whereas larger pocket aneroids were generally supplied together with brass table-type forecasters.
It was precisely this celluloid disc-type foreteller that became the company’s most commercially successful model. The instrument was sold extensively and remained in successful use for many years. Originally retailing at five shillings, it was supplied together with simple printed instructions and a cardboard box embossed in imitation crocodile skin. The The Field issue of 15 February 1936 published a report concerning the instrument’s accuracy, supplied by Ernest Heath of Cornwall, claiming that the foreteller achieved more than 90 per cent accurate forecasts over the course of a year. Such claims may naturally be viewed with caution today; nevertheless, the sheer longevity of production and the vast number of surviving examples clearly demonstrate that the instrument was genuinely regarded by the public as both useful and reliable.
Today, weather foretellers of this type occupy a particularly interesting position for collectors of scientific instruments as well as researchers of early domestic weather-predicting systems. They exist in a unique space between scientific instrument, mechanical calculator, and object of popular science from an era when atmospheric pressure and wind direction were still understood not as abstract meteorological data, but as part of everyday practical observation of the natural world.