HISTORICAL INTRODUCTION

The discovery of magnetism

Mankind's interest in magnetism began as a fascination with the curious attractive properties of the mineral lodestone, a naturally occurring form of magnetite. Called loadstone in early usage, the name derives from the old English word load, meaning “way” or “course”; the loadstone was literally a stone which showed a traveller the way.

The earliest observations of magnetism were made before accurate records of discoveries were kept, so that it is impossible to be sure of historical precedents. Nevertheless, Greek philosophers wrote about lodestone around 800 BC and its properties were known to the Chinese by 300 BC. To the ancient Greeks science was equated with knowledge, and was considered an element of philosophy. As a result, the attractive forces of lodestone were ascribed to metaphysical powers. Some early animistic philosophers even believed lodestone to possess a soul. Contemporary mechanistic schools of thought were equally superstitious and gave rise to false conceptions that persisted for centuries. Foremost among these was the view that electrical and magnetic forces were related to invisible fluids. This view persisted well into the nineteenth century. The power of a magnet seemed to flow from one pole to the other along lines of induction that could be made visible by sprinkling iron filings on a paper held over the magnet. The term “flux” (synonymous with flow) is still found in “magnetic flux density,” which is regularly used as an alternative to “magnetic induction” for the fundamental magnetic field vector B.