In the long eighteenth century, between 1650 and 1820, Wales and the rest of Europe moved from a world of alchemy to one of steam engines and electricity. The scientists of Wales contributed to that changing world of new ideas, but their contribution often overlooked in many histories of the period. This book is a corrective that details the work of scientists from Wales in the four home nations of the isles, covering the intellectual changes of the period and their impact on religion; how scientists were educated in Wales; and, in a lengthy final section, some of the practical science undertaken and the social benefits that resulted.