A column mounted on a rectangular cast iron base holds up a moving arm at the end of which are two spheres representing the earth and the moon. An electric lamp hanging from a column simulates the sun. The arm can be moved with a handle and various gears.
This was a model representing the system formed by the sun, the earth and the moon. The tellurium was used to simulate the movements of the earth and its positions relative to the sun and the moon. This allowed it to enact the succession of the seasons, the change from day to night, the apparent movement of the sun, and when combined with the lunarium, as in this case, the phases of the moon and the eclipses. It was used to teach Cosmography, a subject that was part of the Physics, Mathematics or Geography syllabus, according to the different Secondary Education plans.