Etching by Benjamin Wilson after a portrait by himself. Knight (1713-1772) studied magnetism, and was the leading writer on magnetic fluid theory of his time. In 1748 he observed that the curved lines of iron filings near a magnet describe the paths of magnetic fluids. He produced an improved compas which was adopted by the Royal Navy in 1752. He also became the first principal librarian of the British Museum in 1756.
© Science Museum / Science & Society Picture Library