Barometers Realm

The barometer’s casing consists of a solid plexiglass panel measuring 1 meter in height, 14 cm in width, and 1 cm in thickness. Plexiglass is the trademark name for polymethyl methacrylate (PMMA), a transparent thermoplastic invented in 1933 by German chemist Otto Röhm, co-founder of Röhm & Haas, and marketed under the name Plexiglas®. Around the same time, DuPont developed a similar material in the United States called Lucite, while in the United Kingdom it became known as Perspex. Although methyl methacrylate was first synthesized in 1877 by Friedrich August Kekulé, its practical use was not understood until decades later.

Affixed to the back of the plexiglass panel is the glass tube of a siphon mercury barometer. A small float is located in the lower bend of the tube, connected via a thread to a wheel mechanism, with a counterweight suspended on the opposite side. As atmospheric pressure increases, the mercury level in the lower bend drops, causing the float to descend; the wheel turns to the right, and the indicator needle, mounted on the front of the panel, rotates accordingly. Conversely, when the atmospheric pressure drops, the mercury rises, the float ascends, the counterweight descends, tightening the thread and rotating the wheel to the left.

The barometric scale is printed directly on the casing in the form of a concentric arc and is calibrated in hectopascals. Inside the scale are three Dutch weather descriptors: slecht weer (bad weather), veranderlijk (changeable), and goed weer (good weather).

Two additional instruments are also mounted on the panel: an alcohol thermometer with a Celsius scale and a Tension-fibre hygrometer with a concentric scale for relative humidity in percent.

At the top of the panel is the title “Wielkwikbarometer” — Dutch for “mercury wheel barometer” — along with a hole for wall mounting. For safety and stability, the panel is equipped with four plastic spacers at each corner. These spacers keep the instrument slightly offset from the wall, providing clearance for the delicate mercury tube and associated mechanisms behind the panel.