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S318-26 · Recorders
1935-1955
503
Richard
brass, cast iron, gilding, glass, nickel silver, steel
Object Overview
This Zenith Cabinet Barograph, manufactured by the Swiss Zenith manufacture circa 1935–1955, represents an unusually elegant interpretation of the classic weekly aneroid barograph. The instrument was made in a relatively compact cabinet format and differs markedly from most professional meteorological barographs of its period, not so much in its operating principle as in the exceptional attention paid to materials, finish, and mechanical craftsmanship. Its origins in a watchmaking company are particularly evident in its construction: here, a functional measuring instrument was conceived at the same time as a display of precision mechanics.
The case has a design unusual for a barograph. Instead of the traditional wooden base, it employs a massive cast-iron base finished in black textured enamel. Its stepped profile visually separates the heavy, dark foundation from the light, almost transparent upper part of the instrument. A small ZENITH maker’s plaque is mounted on the front.
The upper part of the case consists entirely of a glass cover held within a tubular brass frame. The large panels are made of thick mineral glass with exceptionally wide and striking bevelled edges around their perimeter. These bevels refract the light and give the enclosure the appearance of a high-quality display case for a precision mechanism rather than an ordinary protective cover for a meteorological instrument. The combination of the massive cast-iron base, thick glass, and brass frame makes the barograph quite heavy despite its compact dimensions.
For servicing, the entire glass cover can be removed. In its working position it is secured to the base by two lateral screws. This arrangement provides unrestricted access to the clockwork drum, the barometric element, and the transmission mechanism.
Inside the case is a horizontal gilt-brass mounting plate carrying almost the entire mechanism. It is engraved ZENITH and No. 503. The clockwork drum is finished in the same golden tone, giving the mechanical assembly a visually unified appearance.
On the left is the rotating weekly drum, around which the paper pressure chart is wrapped. The chart is held in place by a traditional spring-loaded brass clip, which presses it firmly against the cylindrical surface. The upper cover of the drum is removable.
The clockwork mechanism housed inside the drum deserves particular attention. Its construction demonstrates the meticulous finishing and high standard of mechanical workmanship characteristic of the Zenith watch manufacture. The winding key remains permanently fitted directly into the winding arbor of the drum, eliminating the need for a separate removable key.
The most distinctive feature of the drum is a broad circular inspection window covered with mineral glass, through which part of the clockwork mechanism can be seen. Such a feature is entirely unnecessary in a purely utilitarian meteorological recorder and is therefore particularly revealing: it is a characteristically horological gesture, deliberately exposing a small portion of the instrument’s inner mechanics to the observer. Zenith seems almost to invite the viewer to look inside the mechanism it created.
Through the same window, the rate regulator can be seen, marked A/R — avance/retard, indicating adjustment for faster or slower running. The window itself, however, is intended for inspection only; for proper adjustment of the rate, the clockwork mechanism must be removed from the drum.
The barometric sensing element consists of a vertical stack of five 45-mm corrugated aneroid capsules made of nickel silver. Each capsule forms an independent evacuated sensing element and is equipped with its own internal spring, most probably of the disc-spring type. Unlike constructions in which several diaphragms form a common bellows-like assembly, five distinct capsules are clearly identifiable here.
They are connected directly through the rigid central portions of their diaphragms: the lower diaphragm of each successive capsule is screwed, at its rigid centre, onto the upper part of the capsule beneath it. The individual deformations are therefore added together in series, producing a comparatively large resultant vertical displacement of the complete stack.
Decorative brass rings are fitted between the capsules, emphasizing the separation of the individual elements and giving the assembly its characteristic alternating silver-and-gold appearance. A functional component is thus transformed into one of the principal visual features of the instrument — another indication that the aesthetics of exposed mechanics received considerably greater attention here than in a conventional laboratory barograph.
The movement of the upper part of the aneroid stack is received by a system of levers that magnifies the small deformation of the capsules to a displacement sufficient for recording on the chart. The primary lever is balanced by a counterweight; from there, motion is transmitted to a short intermediate lever and then to the long, lightweight recording arm. This kinematic arrangement provides substantial amplification of the sensing element’s movement while imposing only a minimal additional load on the capsule stack.
The recording arm terminates in a characteristic V-shaped reservoir pen, designed to retain a small quantity of recording ink and continuously trace a line on the chart as the drum rotates.
The brass supporting pillars and the components of the transmission mechanism are particularly finely executed. Their form, proportions, and overall arrangement show a noticeable resemblance to the classic mechanisms used in Jules Richard barographs. This is hardly surprising: the highly successful kinematic architecture of Richard’s French barographs was reproduced and adapted by numerous European manufacturers of recording instruments over many decades. In the Zenith, this well-established arrangement received its own exceptionally refined Swiss execution.
The manner in which the individual components are connected is equally characteristic of watchmaking practice. The linkage rods are articulated by means of fine watchmaker’s pins. In operation they remain under slight continuous tension due to the weight of the lever connected to the aneroid capsule stack. This allows the joints to operate with minimal play while maintaining extremely low resistance to movement.
A dedicated pen-lifting device is provided to separate the pen from the chart. It is operated by a small knurled knob. Unlike some professional barographs, however, in which the pen-lifting control is accessible from outside the case, the glass cover of this instrument must first be removed in order to reach the control.
Calibration and adjustment for the altitude of the instrument above sea level are carried out from underneath the instrument. An adjusting screw acts upon the massive brass plate to which the entire aneroid capsule stack is attached. Turning the screw in either direction alters the position and mechanical tension of this support relative to the main mounting plate, thereby shifting the initial position of the sensing assembly and, consequently, the position of the pen on the chart.
This arrangement allows the barograph to be corrected for local atmospheric pressure or its indication to be brought to the required barometric reference without altering the geometry of the principal transmission mechanism.
The Zenith Cabinet Barograph is a rare example of an instrument in which the traditional design of a meteorological recorder was reinterpreted through the standards of high-grade watchmaking. Its operating principle is entirely conventional: a stack of aneroid capsules, lever amplification, a recording pen, and a rotating weekly drum. What is unusual is the manner in which all of these elements were executed.
The heavy black cast-iron base, the all-glass enclosure with its broad bevelled edges, the gilt-brass platform, the silver-toned capsule stack separated by decorative brass rings, the finely turned pillars and linkages, the watchmaker’s pins, and finally the glazed window revealing part of the clockwork transform a technical recorder into a kind of showcase for precision mechanics.
For Zenith, a watch manufacture, even the drive mechanism concealed inside the recording drum became an object of engineering and aesthetic attention in its own right. The inspection window is almost symbolic: the instrument does not merely record changes in atmospheric pressure, but invites the observer to see the mechanics that make this record possible. Barograph No. 503 is therefore significant not only as a mid-20th-century meteorological instrument, but also as an unusual meeting point between two traditions of Swiss precision engineering — meteorology and the art of watchmaking.