Before he was thirty, at the beginning of the nineteenth century, Thomas Weaver was an accomplished engineer and geologist who was successfully managing Avoca's main copper mine and had brought order to the nearby gold workings. He had no ordinary upbringing in Gloucester, where George III had visited his father's factory, and he was sent to study at Freiberg in distant Saxony. Now known as a strict if considerate manager to his Irish workforce, he also participated in suppressing the 1798 Rebellion in Wicklow. He was subsequently active in the mining industry in both Ireland and Mexico. In parallel, he carried out geological mapping in these countries as well as in Great Britain and North America. He was an engaging personality, someone who would partake as enthusiastically in a local ploughing contest as in a scholarly debate in London. His story sheds light on industrial and social conditions in pre-Famine Ireland and elsewhere. It is a story worth telling. He was active at a time when geology was coming of age as a scientific discipline. Science is described as a journey without destination, where theories are constantly challenged and remain valid only until they are undermined by new evidence. Yet, as the current climate change debate shows, there can be an alarming intolerance for the very dissent that should be critical to validating its conclusions. This proved to be the case in Weaver's lifetime. For he also took issue with emerging new mindsets and was eventually marginalized as a result. This book will appeal to anyone interested in the science and industry of the early nineteenth century, as well as for students of the philosophy and history of science.