Experiments in Electricity

Benjamin Franklin’s book, Experiments and Observations on Electricity, is one of the most important scientific treatises of the 18th century, the founding work on the new science of electricity. One reason why Franklin’s book was so popular and why he became one of the most famous scientists of his age was, of course, his lightning experiments and invention of the lightning rod. Most history books limit their presentation of Franklin’s research in electricity to a single experiment––the celebrated electric kite. This not only denies Franklin his role in the creation of modern electrical science, but reduces his magnificent contribution to a single experiment that was not in any case Franklin’s fundamental experiment on lightning. Most accounts make it appear that his research, including the kite experiment, was a test to see whether the lightning discharge is an electrical phenomenon, but––as readers of Franklin’s book will quickly discover––what he was testing was something quite different, namely, whether clouds are electrified.
Franklin’s book also presented a large variety of new experimental discoveries concerning the ways in which bodies gain or lose electrical charges, and it also explored a range of phenomena we would call electrostatic induction. One of his achievements was to analyze the action of the recently discovered “Leyden jar,” the first capacitor or condenser––Franklin’s analysis was hailed as a major discovery because the scientific world was puzzled by such a simple device producing so tremendous an effect. Above all, Franklin clearly showed the effects of grounding in making electrical experiments, and he produced the first major theory of electrical action, explaining and predicting the outcome of electrostatic manipulations in the laboratory. Franklin’s book also introduced the language we still use in discussing electrical phenomena, including plus or positive, minus or negative, and electrical battery.
Commentary by I. Bernard Cohen, searchable live text.