At the end of the 17th century, magnetism was a dark, mysterious force. Edmond Halley set out to map the Earth's magnetic patterns and improve navigation, showing how science could help England to expand her empire. Gowin Knight climbed to fame and fortune by developing powerful artificial magnets used in compasses, scientific experiments and popular magic tricks. And although Franz Mesmer claimed that his 'animal magnetism' was the revolutionary medicine of the future, he was ultimately denounced as a quack.