Benjamin Franklin, journeyman printer and journalist, statesman and diplomatist, was about sixty years old when Priestley, then a man of little more than half his age, first made his personal acquaintance. The Royal Society, which had formerly ridiculed the discoveries which have given Franklin his undisputed position as one of the most eminent natural philosophers of his time, had paid him, although still a British subject, the distinguished compliment of making him an honorary fellow. At the time of Priestley’s coming to town he was occupied with the great struggle on behalf of the American Colony which ended in the defeat of the Stamp Act, and his famous examination before a Committee of Parliament had made him an object of great popular interest. During the eight or nine succeeding years in which Franklin remained in England his acquaintance with Priestley grew into the closest friendship, and there can be no question that the friendship reacted powerfully on Priestley’s work as a political thinker and as a natural philosopher. Indeed, it may be truthfully said that Franklin made Priestley into a man of science. As the result of this intercourse with Canton and Franklin, Priestley offered to compile what he called “a distinct and methodical account” of the history of discoveries in electricity, provided he could be supplied with the necessary books. Franklin warmly seconded the proposal, and undertook, with the assistance of friends, to furnish all existing literature on the subject. As a matter of fact almost the whole of the historical account in Priestley’s book is taken from the _Philosophical Transactions of the Royal Society_, which was then the chief source of information concerning electrical science, inasmuch as the English electricians of that period, in addition to their own original papers, which were both numerous and important, introduced into the _Transactions_ detailed accounts of all the principal books on electricity published abroad. In putting together his work, Priestley, having, as he says, a pretty good machine, was led to endeavour to ascertain several facts which were in dispute, and was thus led by degrees into a large field of experimental inquiry, in which he spared no expense that he could possibly afford. One of the most important of his discoveries is that charcoal is a good conductor. He describes coloured circles produced by receiving discharges from 21 square feet of glass on metal plates. When an electrical battery is discharged light bodies placed near the electric circuit are moved. Priestley ascribes this motion to what he calls the force of the lateral explosion, and he conceives it to depend upon the sudden elasticity given to the air. He found that a long circuit conducts much worse than a short circuit, even when the conductors are the same; also, that when the circuit contains an imperfect conductor a spark passes to bodies near, no electricity being communicated.