Inside the book

The treatise is divided into four parts, reflecting the author's conviction that the science could be presented with full rigour only by separating established fact from hypothesis, and both from practical instruction. Part I, "Fundamental Laws of Electricity," treats basic terminology, electrics and conductors, positive and negative electricity, methods of excitation, communicated electricity, the Leyden phial, atmospheric electricity, practical advantages, and a summary of principal properties. Part II, "Theory of Electricity," is expressly hypothetical, with the preface noting that this section relates "not to facts, but to opinions" and that the "great improbability of most of these hypotheses" kept it brief. Part III, "Practical Electricity," covers apparatus, machine design, components, experimental setup, attraction and repulsion, electric light, the Leyden phial, charged electrics, lightning conductors, the electrical battery, and further properties of the Leyden phial. Part IV, "New Experiments in Electricity," presents the author's contributions: the electrical kite and kite experiments, atmospheric and rain electrometers, the electrophorus, a machine for producing perpetual electricity, experiments on colours, and promiscuous experiments. The introduction traces the history from Theophrastus and amber through William Gilbert (hailed as the father of the science), Boyle, Otto von Guericke, Newton, Hawkesbee, and Stephen Grey, whose rediscovery marks the "true flourishing era." The three folding copperplates, engraved by John Lodge after drawings by T. Conde, depict machines, Leyden jars, electrometers, conductors, kite apparatus, and related instruments. The work went through three further editions in the author's lifetime, the second in 1782 and the third in three volumes between 1786 and 1795, each substantially enlarged, and remained a standard reference for both neophytes and advanced experimenters.