De Magnete - Contents

Contents

In this work, Gilbert described many of his experiments with his model earth called the terrella. From the experiments, he arrived at the remarkable (and correct) conclusion that the Earth was magnetic and that this was why the compass pointed north. (Previously, it was thought that Polaris or a large magnetic island at the North Pole attracted the compass). Gilbert also made the claim that gravity was due to the same force and he believed that this held the Moon in orbit around the Earth. While incorrect by modern standards, this claim was still far closer to the truth than the ancient Aristotelian theory, which held that the heavenly bodies consist of a special fifth element which naturally moves in circles, while the earthly elements naturally move downward. Johannes Kepler accepted Gilbert's theory and used it as a working basis for his famous laws of planetary motion.

In De Magnete, Gilbert also studied static electricity produced by amber. Amber is called elektron in Greek, and electrum in Latin, so Gilbert decided to refer to the phenomenon by the adjective electricus, giving rise to the modern terms 'electric' and 'electricity'.

De Magnete was influential not only because of the inherent interest of its subject matter, but also for the rigorous way in which Gilbert described his experiments and his rejection of ancient theories of magnetism. Gilbert nevertheless acknowledged his debt to Peter of Maricourt and incorporated this thirteenth-century scientist's experiments on magnetism into his own treatise. Although Gilbert's thinking was influenced by the mysticism of his time, Gilbert is regarded as a pioneer of experimental science.