Due to the high sensitivity of the instrument, Eötvös was able to determine the magnetic momentum of rocks and other bodies of weak magnetism. He carried out similar measurements on old bricks and clay pots. During the firing and cooling of the bricks and pots, several hundred years ago, they acquired a remanent magnetization in the direction of the ambient magnetic field. Since it was easy to recognize the sides of the bricks and the bottoms of the pots on which they had rested during firing, it was possible to stand them up in the same position. After having determined the direction of their magnetic momentum, the inclination of the magnetic field at the time of their cooling could be defined.