Barometers Realm

In the mid-17th century, a charming weather instrument known as the Cartesian diver became well-known. It was also called the Cartesian devil, Descartes’ float, Descartes’ diver, and Tanzteufel — the dancing devil. It was described by Raffaello Magiotti, an Italian physicist and astronomer, in his work Renitenza dell’acqua alla compresse, published in 1648. The Cartesian diver became an illustration of the principles of buoyancy and the ideal gas law. Essentially, the little devil demonstrated a remarkable relationship between pressure and buoyancy. Test In 1654, Athanasius Kircher, a German scholar and inventor, used handmade glass figurines depicting scenes from the Annunciation and the Ascension of Christ, and later introduced the diver-devil figurine. This became a popular toy. Such a figurine was placed in a flexible container with water. When the flexible part of the container was squeezed, the figurine would dive due to the increased pressure inside the container, causing the diver to sink to the bottom. When the pressure on the container walls was released, it would rise back to the surface. According to Pascal’s law, compressing a sealed container increases the air pressure exerted on the water, which in turn applies additional pressure on the air bubble inside the diver.

If the container was rigid, like a glass bottle, the seal was achieved by quickly covering the opening with the palm, thereby altering the pressure inside the container. For better results, various membranes were used due to the flexibility of their walls, such as a pig’s bladder.

The toy devils were made with a tail coiled around their bodies, through which water could flow inside when the pressure increased and flow out when it decreased. These devils would start spinning when the pressure periodically changed. The figurines inside the vessel literally danced under the influence of changing pressure, which apparently inspired the name "dancing devil".

Here is a modern interpretation of this invention: a glass devil, handcrafted in the 2020s. It stands about 5 centimeters tall and is made of colored glass. The body is a deep blue, while the limbs, horns, and face are dark green, creating the impression of an ancient artifact, as if it had come to us from the past.