The only sources of information hitherto available about Joseph Henry, probably the greatest 19th-century American scientist, consisted of a number of scattered magazine articles, the "Memorial" collected after his death and published by order of Congress in 1880, and short accounts in various histories of science, among which Crowther's seventy-page narrative (in Famous American Men of Science) is the most complete. The task of writing a full-scale biography of Henry has thus long been incumbent upon American historians: in this task, Mr. Coulson has succeeded most admirably.
• Joseph Henry died in 1878 at the ripe age of eighty-one, after a lifetime of unflagging industry and remarkable achievement--but the discoveries which brought him international fame were made largely before he was thirty-five. He was a teacher at the Albany Academy when he discovered mutual induction (contemporaneously with Faraday, who published his results first and is consequently acknowledged as the discoverer); and he was still at Albany when he announced his greatest single contribution to science, the discovery of self-inductlon.
It is an interesting commentary on the limited circulation of American scientific journals in Europe at this time that Faraday was apparently not aware of Henry's work, for two years later the British scientist announced his observation of the phenomenon of self-induction as an original discovery. But world-wide recognition came to Henry before long, and when the International Congress of Electricians met in Chicago in 1893, the suggestion of two foreign representatives (from France and Britain) to give the name "henry" to the standard unit of inductance was adopted unanimously.
Henry's great early contributions have tended to overshadow his later work. Mr. Coulson points out that Henry developed the electromagnetic relay, drew attention to the utility of the transformer, investigated the effects of electromagnetic shieldlng, and was the first to establish the oscillatory nature of an electric discharge through an inductance (which is the basis for radio transmission). After he was appointed to a professorship at Princeton, he also studied the phenomena of capillarity, phosphorescence, and atmospheric electricity. He made important contributions to the science of meteorology and started an investigation of the correlation of natural forces which led him to the very brink of the concept of conseI:vation of energy. He was at the peak of scientific endeavor when the offer to become secretary of the newly formed Smithsonlan Institution was brought to him. He considered the proposal briefly, not without misgivings, and decided that he could serve the cause of American science best by accepting the post--realizing all the while that he was, as he himself put it, "sacrificing future fame to present reputation." The thirty-two years of his secretaryship saw the Smithsonian rise from a vague clause in an Englishman's will to a world-famous center of scientific activity and clearinghouse of scientific information. The present reputation of the Institution is perhaps the best memorial to Joseph Henry: si monumentum requiris, circumspice.
Mr. Coulson, who is director of museum research at The Franklin Institute, has been able to uncover a good deal of new material through his study of the manuscript resources of the Smithsonian, and he has done an excellent job of bringing together the scattered scraps of information previously available. He has not hesitated to point out some of the limitations of Henry, who was largely an experimental scientist and, in Mr. Coulson's words, "probably the last physicist to attain international fame by the use of simple arithmetic