In the lead-mining area of the Mendip Hills in Somerset in the 17th century the natural philosopher Robert Boyle, inspired by the writings of Agricola, watched a practitioner try to find latent veins of metals. Boyle saw the hazel divining rod (virgula divinatoria) stoop in the hands of the diviner, who protested that he was not applying any force to the twig; Boyle accepted the man's genuine belief but himself remained unconvinced.