Purſuits of a different nature now occupied the greateſt part of his attention for ſome years. He engaged in a courſe of electrical experiments, with all the ardor and thirſt for diſcovery which characterized the philoſophers of that day. Of all the branches of experimental philoſophy electricity had been leaſt explored. The attractive power of amber is mentioned by Theophraſtus and Pliny, and, from them, by later naturaliſts. In the year 1600, Gilbert, an Engliſh phyſician, enlarged conſiderably the catalogue of ſubſtances which have the property of attracting light bodies. Boyle, Otto Guericke, a burgomaſter of Magdeburg, celebrated as the inventor of the air pump. Dr. Wall, and Sir Iſaac Newton added ſome facts. Guericke firſt obſerved the repulſive power of electricity, and the light and noiſe produced by it. In 1709, Hawkeſbee communicated ſome important obſervations and experiments to the world. For ſeveral years electricity was entirely neglected, until Mr. Grey applied himſelf to it, in 1728, with great aſſiduity. He, and his friend Mr. Wheeler, made a great variety of experiments; in which they demonſtrated, that electricity may be communicated from one body to another, even without being in contact, and in this way may be conducted to a great diſtance. Mr. Grey afterwards found, that, by ſuſpending rods of iron by ſilk or hair lines, and bringing an excited tube under them, ſparks might be drawn, and a light preceived at the extremities in the dark. M. Du Faye, intendant of the French king's gardens, made a number of experiments, which added not a little to the ſcience. He made the diſcovery of two kinds of electricity, which he called vitreous and reſinous; the former produced by rubbing glaſs, the latter from excited ſulphur, ſealing-wax, &c. But this idea he afterwards gave up as erroneous. Between the years 1739 and 1742, Defaguliers made a number of experiments, but added little of importance. He firſt uſed the terms conductors and electrics, per ſe. In 1742, ſeveral ingenious Germans engaged in this ſubject. Of theſe the principal were, profeſſor Boze of Wittemberg, profeſſor Winkler of Leipſic, Gordon, a Scotch Benedictine monk, profeſſor of philoſophy at Erfurt, and Dr. Ludolf of Berlin. The reſult of their reſearches aſtoniſhed the philoſophers of Europe. Their apparatus was large, and by means of it they were enabled to collect large quantities of electricity, and thus to produce phenomena which had been hitherto unobſerved. They killed ſmall birds, and ſet ſpirits on fire. Their experiments excited the curioſity of other philoſophers. Collinſon, about the year 1745, ſent to the library company of Philadelphia an account of theſe experiments, together with a tube, and directions how to uſe it. Franklin, with ſome of his friends, immediately engaged in a courſe of experiments; the reſult of which is well known. He was enabled to make a number of important diſcoveries, and to propoſe theories to account for various phenomena; which have been univerſally adopted, and which bid fair to endure for ages. His obſervations he communicated, in a ſeries of letters, to his friend Collinſon; the firſt of which is dated March 28, 1747.