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S335-26 · Recorders
c.1930
Object Overview
This weather-forecasting barograph, known as the Cyclo-Stormograph, was made around 1930 by the renowned London firm of Short & Mason. The case bears no Short & Mason marking, and the instrument was evidently made to the order of another firm. A chart from the Liverpool firm of J. Sewill Ltd has survived with the barograph. Sewill was a maker of marine chronometers and navigational instruments known since the nineteenth century and a supplier to the Admiralty. This suggests that Sewill commissioned or retailed the instrument, although this has not been conclusively confirmed. Such practice was common at the time: major manufacturers produced instruments for trading houses and specialist firms, which then sold them under their own names. The attribution to Short & Mason is nonetheless beyond doubt, since the mechanism embodies a design protected by the firm's patents, above all Patent No. 22556 of 1904 for a barograph with a concealed vacuum chamber.
The name of the instrument combines the words , and ("writing"). It reflects the instrument's dual purpose: the Cyclo-Stormograph not only records atmospheric pressure continuously but also allows the weather to be forecast from the record. The underlying idea is that a forecast can be made from the pressure reading alone and whether it is rising or falling. For this purpose a special chart is used, on which letters are printed alongside the inch scale of pressure. A legend plaque on the base of the instrument assigns a weather forecast to each interval between the letters, separately for a falling and a rising line.
aneroid capsule tensioned on a C-spring
brass, cast iron, glass, paper, steel, wood
The case is substantial, made of solid oak, and consists of two parts: a base and a removable glazed cover. The base is stepped, with a moulded edge, and stands on four turned feet. The cover, in an oak frame, is glazed on all sides with flat mineral glass. The case measures 37 × 22 × 18 cm. The clock drum is mounted on the left of the base, and on the right is the visible part of the recording mechanism with its shaped pillars and pen arm.
An interesting addition is a glass ink bottle with a brass dipper set in the stopper. It sits in a recess at the rear of the base, framed by a brass flange, so that it is always at hand and protected from being knocked over.
The clock drum follows a patented arrangement that differs from the conventional one. In ordinary barographs the clock movement is enclosed within the cylinder and is removed together with it. Here the clock movement is mounted separately and fixed to the case, while the light brass drum fits over it from above. When the drum is lifted off to change the chart, the clock movement stays in place. This makes servicing easier and spares the movement unnecessary handling and jolts.
The clock movement was made by Rotherham & Sons of Coventry, the oldest watch and clockmaking firm in the city. This is shown by the "R&S" stamp together with "Made in England" on the platform escapement; the mark was registered at the London Assay Office in 1907 for Rotherham & Sons. The use of an English platform is consistent with the dating of the instrument: in 1929 Rotherham's became the first English clockmaking firm to produce an all-English platform escapement movement.
The drum is fitted with a brass clip to hold the chart. This too differs from the usual spring clip: it carries a tiny swivelling lever. Once the chart is pressed in place, the lever is turned so that it bears against the wall of the drum, holding the clip securely.
The chart is weekly, starting on Sunday, with a pressure scale from 28 to 31 inches of mercury divided into 0.10-inch intervals. The time lines are curved to follow the arc described by the pen. Letters from A to K are printed alongside the pressure scale at intervals of 0.30 inch: A corresponds to 31.00 inches, B to 30.80, C to 30.50, D to 30.20, E to 29.90, F to 29.60, G to 29.30, H to 29.00, I to 28.70, J to 28.40 and K to 28.10. To interpret the readings, a legend plaque (not original) mounted on the instrument reads "Weather Forecast. Approximate weather readings as indicated by various sections of the S. & M. Cyclo-Stormograph Chart".
The mechanism is unusual: the vacuum chamber and the first link of the transmission are housed beneath the base plate and concealed within the case. It is based on a single corrugated metal aneroid capsule held under tension by a C-shaped steel leaf spring, which is mounted on a heavy cast-iron bridge. This is the same arrangement as in a conventional aneroid barometer movement, but here it is inverted through 180 degrees and sunk into the wooden base of the barograph.
The main lever, extending from the free upper end of the C-spring, transmits the motion in the usual way via a link to the next stage, a two-armed lever. Here, however, the link passes through the brass base plate to the visible part of the mechanism. There the two-armed lever is pivoted between centres. Its long arm is connected by a second link to the angled lever of the main arbor, also pivoted between centres, and the pen arm is mounted on this arbor. The pen arm is carried on a swinging gate suspension that reduces friction. At the end of the arm is a V-shaped trough pen.
The barograph is fitted with a pen-lifting device operated by a small lever at the front of the base, accessible once the glass cover is removed. The lever moves the pen away from the drum, making it easier to change the chart and preventing accidental marks.
The altitude adjustment is located at the front of the brass base plate. It takes the form of a knurled knob; turning it shifts the position of the cast-iron bridge concealed beneath the plate and thereby moves the pen along the pressure scale.
The Short & Mason Cyclo-Stormograph combines the engineering ingenuity of the early twentieth century with a practical purpose. Because the vacuum chamber is concealed, the space beneath the cover is left open, giving the instrument a distinctive lightness: only the elegant brass levers, the drum and the ink bottle are on view. At the same time the vacuum chamber is fully enclosed and thus protected from damage, which was one of the aims of the 1904 patent. The lettered-chart forecasting system turned the barograph from a meteorologist's instrument into a practical household device, allowing its owner to judge the coming weather without any specialist knowledge.