This collection of primary sources examines scientific methodology in Britain during the long nineteenth century. The nineteenth century begins with what was still a largely Newtonian perspective on the nature of matter and the physical world – Newtonian bodies moving through space, guided by a collection of forces, with gravity foremost among them. By the end of the century, physical science had refocused itself around the concept of energy, the first moves toward the understanding of atomic structure had been undertaken, and electricity and magnetism were understood in terms of fields of force. This volume examines primary sources related to the philosophy of the physical sciences, and will be of great interest to students of the history of philosophy and the history of science.