Barometers Realm

This Travel Weather Telegraph, circa 1927, by the renowned firm Wilhelm Lambrecht of Göttingen, is an instrument that provides reliable weather forecasts by purely mechanical means, without any difficulty of observation. All calculations are entirely eliminated, thereby making the preparation of a forecast extraordinarily simple: it is sufficient merely to determine the relative positions of two pointers within the table mounted on the apparatus and to read directly the corresponding forecast displayed alongside.

The travel weather telegraph represents a compact version of the Wettertelegraph (Weather Telegraph), an instrument that formed an integral part of Lambrecht’s celebrated Wettersäulen (Weather Columns), which from the mid-19th century awakened, satisfied, and sustained public interest in atmospheric phenomena. At the same time, these columns served as ornamental features of their surroundings and were therefore endowed, to a greater or lesser extent, with artistic decoration.

Why did Lambrecht call his instrument a Weather telegraph? What does the telegraph have to do with it at all? Below, an unexpected answer to this question awaits.

All components of the weather telegraph are mounted in a compact wooden case, externally covered in black leather. The measuring instruments are installed directly into the lid of the case, while the prognostic table is located in the lower section. The interior of the lower half of the case is lined with purple velvet and includes a pocket for the accompanying magnifying glass, intended to facilitate more precise reading of the scales and prognostic symbols.

In the lid of the case, mounted on a thick brass plate painted black, are three meteorological instruments: a thermohygroscope, a minimum–maximum thermometer, and an aneroid barometer.

The thermohygroscope is a complex combined system uniting a bimetallic thermometer and a hair hygrometer into a single measuring element. From the bimetallic spiral of the thermometer extends a natural human hair, which first passes through a knurled regulating nut, then connects to the indicating pointer, and finally to a characteristic “bow”-like element that provides the necessary working length and tension of the hair. This “bow” moves together with the pointer, as both elements are mounted on the same shaft. The upward movement of the pointer along the scale engraved on the silvered brass dial indicates dry and stable weather, while its downward movement foreshadows precipitation and deteriorating weather conditions. The measuring mechanism is enclosed in a nickel-plated brass case, and the dial is protected by flat faceted mineral glass.

The maximum–minimum thermometer consists of two separate mercury capillaries: the left records minimum temperatures, while the right records maximum values. The capillaries are mounted on a single plate of opaline glass bearing scales in degrees Celsius, ensuring excellent legibility and long-term durability of the markings.

The aneroid barometer is housed in a cylindrical nickel-plated brass case and fitted with a rotating knurled bezel that secures flat mineral glass with a faceted edge. Rotation of the bezel adjusts an altitude scale in meters, ranging from −200 to +2600 m. The barometer dial is made of silvered brass and carries a barometric scale in centimeters of mercury, ranging from 56 to 78 cm. The instrument is driven by a temperature-compensated conventional movement with a 30-mm aneroid capsule tensioned by a C-shaped steel spring; motion is transmitted to the pointer shaft by means of a fusee chain. A particularly noteworthy detail is the use of blued screws, which have retained their metallic sheen, while other steel components have suffered noticeable corrosion.

The final element mounted in the lid of the case is the marking plate. This serves to record the positions of the pointers of the measuring instruments at a given moment, after which the corresponding forecast can be read from the table. The table itself is printed on a thick enamelled plate located in the lower part of the case and held in place by a black-painted brass frame.

Using only two pointers, the weather telegraph displays the three principal factors determining the weather: air temperature, air humidity, and atmospheric pressure. The various states arising from the changing interaction of these factors are explained through combinations of pointer positions on the marking plate, following the model of early optical telegraphs. As a result, even a completely untrained observer can immediately recognize the forthcoming weather conditions.

This refers to the so-called semaphore principle, in which a limited number of mechanical positions of pointers or levers forms a code that any person can “read” using a table. In Lambrecht’s weather telegraph, this function is fulfilled by the marking plate with two pointers—one for the thermohygroscopic element and the other for the barometer—which generate specific combinations, accompanied by an adjacent ready-made “decoding” in the form of a textual forecast.

In semaphore telegraphs (pre-electrical systems of communication), messages were transmitted visually: on towers or masts stood a mechanism with movable arms or indicators (sometimes multiple “wings”). The operator set a particular configuration of these elements, and an observer at the next station viewed the configuration through a telescope or binoculars and compared it with a code table to obtain a letter, number, or phrase; the configuration was then relayed further along the chain of stations.

Lambrecht employs precisely the same interface concept, except that the “message” is not created by a human operator, but by the atmosphere itself. Two pointers—the barometric pointer and the pointer linked to humidity and dew point via the thermohygroscope—can assume various positions. Together they produce numerous combinations, analogous to two “semaphore wings.” There is also an “alphabet” of combinations, and the states are explained by Zeigerbilder—“pointer images,” that is, standardized illustrations of pointer positions. This constitutes the equivalent of a semaphore “code.” Finally, a “decoder” is provided in the form of textual forecasts corresponding to each pointer configuration on the marking plate. This is exactly the same concept as in the optical telegraph: one need not be an engineer or a meteorologist—the table makes the observer a reader of the code. This is why Lambrecht uses the word telegraph in the name of the instrument, a choice that is also marketing-perfect: the device appears to “transmit a message” about the weather in a clear, public, and easily intelligible language.

Overall, this travel weather telegraph represents a rare and technologically advanced example of a portable meteorological station for its time, in which engineering precision, visual clarity of forecasting, and carefully considered ergonomics are united in a compact and elegant instrument, intended both for practical use and for the demonstration of the achievements of early 20th-century scientific instrument making.