ELECTROSTATIC INSTRUMENTS BEFORE 1800 123 INSTRUMENTING VOLTAIC OR GALVANIC ELECTRICITY, 1800-1820 124 ELECTRICAL INSTRUMENTATION, 1800-1820 125 OERSTED'S DISCOVERY 126 BEGINNINGS OF ELECTROMAGNETIC INSTRUMENTATION 126 CHRONOLOGY AND PRIORITY 127 ORIGINAL ELECTROMAGNETIC MULTIPLIERS 129 CONCLUSIONS 135 ACKNOWLEDGMENTS 136 [Illustration: Figure 1.--MODELS OF VARIOUS ELECTROMAGNETIC INSTRUMENTS created by Schweigger, Poggendorf and Cumming in 1821, made for an exhibit in the Museum of History and Technology, Smithsonian Institution. (Smithsonian photo 49493.)] _Robert A. Chipman_ THE EARLIEST ELECTROMAGNETIC INSTRUMENTS _The history of the early stages of electromagnetic instrumentation is traced here through the men who devised the theories and constructed the instruments._ _Despite the many uses made of voltaic cells after Volta's announcement of his "pile" invention in 1800, two decades passed before Oersted discovered the magnetic effects of a voltaic circuit. As a result of this and within a five-month period, three men, apparently independently, announced the invention of the "first" electromagnetic instrument. This article details the merits of their claims to priority._ THE AUTHOR: _Robert A. Chipman is chairman of the Department of Electrical Engineering at the University of Toledo in Toledo, Ohio, and consultant to the Smithsonian Institution._ Electrostatic Instruments before 1800 It is the fundamental premise of instrument-science that a device for detecting or measuring a physical quantity can be based on any phenomenon associated with that physical quantity. Although the instrumentation of electrostatics in the 18th century, for example, relied mainly on the phenomena of attraction and repulsion and the ubiquitous sparks and other luminosities of frictional electricity, even the physiological sensation of electric shock was exploited semiquantitatively by Henry Cavendish in his well-known anticipation of Ohm's researches. Likewise, Volta in 1800[1] described at length how the application of his pile to suitably placed electrodes on the eyelids, on the tongue, or in the ear, caused stimulation of the senses of sight, taste and hearing; on the other hand, he reported that electrodes in the nose merely produced a "more or less painful" pricking feeling, with no impression of smell. The discharges from the Leyden jars of some of the bigger frictional machines, such as van Marum's at Leyden, were found by 1785 to magnetize pieces of iron and to melt long pieces of metal wire.[2]