Title page to 'Physica Subterranea', 1738.
© Science Museum / Science & Society Picture Library
Title page from the 1738 edition of 'Physica subterranea' ('The Physics of Things beneath the Earth') by Johann Joachim Becher (1635-1682). This edition of the work which was originally published in 1667, includes Becher's alchemical ideas and experiments on the nature of minerals and other substances. His concept that a 'terra pingus' (oily earth) causes fire was later became the basis of the theory of phlogiston. Becher is not only famous for his theory of combustion but is notable as a technologist, miner and metallurgist. He was the author of a number of books both practical and symbolic and was equally an alchemist and a chemist.