Athanasius Kircher, Jesuit scholar 1602-1680. Coloured portrait after an engraving of the author from Mundus Subterraneus (1664). Kircher worked and published across a remarkable range of fields, and won worldwide fame as a scholar even in his own lifetime. His great museum of naturalia in Rome was unrivalled. In Mundus Subterraneus he considered fossils, volcanoes and the earth's geologic structure, as well as everything from dragons to giants. He believed fossils could be mineralised organic remains, but that also many simply formed inside stones due to an active 'plastic spirit' that gave shape to things. He was also one of the first to observe microbes through a microscope and propose that plague (Yersinia pestis) was caused by infectious microorganisms in the blood. This insight made him among the first to suggest sensible measures to counter the spread of the dread disease.