2012 Reprint of 1904 Edition. Exact facsimile of the original edition, not reproduced with Optical Recognition Software. Illustrated. In the "War of Currents" era in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over alternating current (AC) advocated by several European companies and Westinghouse Electric based in Pittsburgh, Pennsylvania. Alternating current had first developed in Europe. Westinghouse was willing to invest in the technology and hired William Stanley, Jr. to work on an AC distribution system using step up and step down transformers of a new design in 1886. After Stanley left Westinghouse, Oliver Shallenberger took control of the AC project. Nikola Tesla joined the team after 1888. Tesla partnered with Westinghouse Electric to commercialize his particular AC system. Westinghouse had previously bought the rights to Tesla's polyphase system patents and other patents for AC transformers. This is one of Tesla's more important lectures on the subject.