In 1840, an Oxford professor of physics bought an outlandish device consisting of two long, sulfur-coated cylinders connected to two bells. Between the bells a metal ball oscillates, it is driven by the charge of batteries, which are of the dry cell type. In them, unlike modern batteries, the electrolyte, that is, the substance that conducts the charge, is a paste, not a liquid. The bell was created just 40 years after the invention of the first batteries. Its power supply was expected to last about 4 or 5 years. It is amazing that it has been working for almost two centuries.
What was the original essence of the experience with this electric call, and whether it was an experiment at all or just a demonstration, is no longer known for sure. However, at the moment, physicists would be happy to know how the power supply in this bell works, but, unfortunately, the cylinders are sealed and the technical documentation has long been lost. However, there are several considerations in this regard. The fact is that other dry batteries, created at that time, consist of many metal disks stacked on top of each other and filled with sulfur. On the one hand, the discs are coated with zinc sulfate, on the other - with manganese dioxide. Today, zinc sulfate is more commonly used as a bioactive food additive, but manganese dioxide is still used in dry batteries. In the past, somehow managed to make the batteries last incredibly long. However, until we open the Oxford bell cylinders, we will not know how everything works there. Scientists are not in a hurry to open the call. First they want to know how long it will last, but once it stops working, physicists will quickly perform an autopsy on it.