John Hopkinson (1849–98) was a British electrical engineer who invented the three-wire system for the distribution of electricity. Originally published in 1901, this book forms the second of two volumes of Hopkinson's papers, focusing mainly on scientific areas. The text also incorporates editorial notes and numerous illustrative figures. Material of a more technical nature can be found in the first volume. This book will be of value to anyone with an interest in Hopkinson, engineering and the history of science.