William Gilbert

Who Made A Little Earth Of Stone · Physician & Natural Philosopher · 1544–1603

The Queen's physician who spent seventeen years testing everything ever written about the loadstone, found most of it fable, and discovered by grinding one into a sphere that the Earth itself is a great magnet.

Who was Gilbert?

William Gilbert was born at Colchester in 1544, took his degrees at Cambridge, practised medicine in London, became President of the College of Physicians and physician to Queen Elizabeth I. For seventeen years, at his own expense, he tested the accumulated literature of the loadstone and found it largely worthless: garlic does not destroy a magnet's virtue, a diamond does not steal it, it does not heal wounds or reconcile spouses. What he did instead was to grind a loadstone into a true sphere, which he called a terrella — a little earth — and to walk a small pivoted needle over its surface. The needle points along the surface as a compass does, and it dips downward as it approaches the pole exactly as Robert Norman's dipping needle does over the real Earth. The conclusion of De Magnete, published in 1600, follows: the compass needle is not drawn by the pole star nor by any island of loadstone in the north, but by the globe under our feet, which is itself a magnet. He established that iron can be magnetised by stroking and by hammering while aligned north-south, that heating destroys the magnetism, and that magnetic attraction passes through interposed bodies. He also distinguished sharply between the magnetic virtue and the amber effect — which he named electric, from the Greek for amber — showing that many substances besides amber attract light bodies when rubbed, that this differs from magnetism in every respect, and building a light pivoted straw, the versorium, to detect it. He was an early Copernican, on magnetic grounds, and held that the Earth possessed a magnetic soul.

Major achievements

• Discovered that the Earth is a magnet, by grinding a loadstone into a sphere and testing a needle on it
• Explained the dip of the compass needle and its direction from that single hypothesis
• Demolished the folklore of the loadstone by systematic experiment
• Distinguished the magnetic effect from the amber effect and named the latter electric
• Built the versorium, the first instrument for detecting electric attraction

Life in brief

• 1544 — Born at Colchester: Son of the town recorder.
• 1569 — Doctor of medicine at Cambridge: Then practice in London.
• 1580s — Seventeen years of experiments: At his own expense, on the loadstone.
• 1600 — De Magnete: The Earth declared a magnet; the word electric coined.
• 1600 — President of the College of Physicians: And physician to the Queen.
• 1603 — Dies in London: Probably of plague, months after the Queen.

Explore the life of Gilbert — five chapters

1. Physician to the Queen — A respectable career, and seventeen years of private experiment
2. The Little Earth — A loadstone ground into a sphere
3. Coining the Word Electric — And insisting the two effects have nothing to do with each other
4. De Magnete — 1600, and one of the first books of experimental science
5. What Came of It — Kepler, Galileo, Bacon's objection, and plague

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