^* The following brief description may be helpful to students. The sections mentioned were almost ready, and would need comparatively little revision before publication. The guiding purpose of the book was to trace in a concrete and important historical instance the considerations which lead a scientist to adopt conventions. A logical analysis of the notions associated with the classical notion of electrical ‘field’ leads Bowdery to formulate eight conclusions with respect to the role of definitions and fictions in the theory. The subsequent discussion of “The Background of Maxwell's Theory” is both analytic and historically descriptive. It brings together interesting and relatively unknown materials for this significant episode in the history of science.