Ceasing his account of his military experiences, Franklin turns to his scientific achievements. In 1746, Franklin receives instruction in the conducting of scientific experiments. He manufactures a number of beakers and practices his own experiments at home. Franklin slowly develops the idea that lightning and electricity are the same thing, an idea which is at first laughed upon by many well known scientists. Franklin publishes his experiment papers, which include mention of his now- famous kite experiment. The papers are immediately translated into several languages; Franklin quickly gains extraordinary celebrity status. He receives a medal of honor from the Royal Society, a very prestigious award. Meanwhile, Franklin develops his friendship with the new Pennsylvania Governor, Capt. Denny, who entertains Franklin at dinners from time to time.
The Pennsylvania Assembly, in 1756, appoints Franklin as the Commissioner to England, where he must travel in order to press for colonial rights with the Crown in accordance with a petition put together by the Assembly. Franklin is chosen for the job largely because of his scientific reputation overseas. Franklin meanwhile worked towards provisions for the further defense of the colonies. He keeps track of the events of the war, which end up going very well for the British troops several years into the war. Franklin also comments extensively on which military figures he respected and which he thought lackluster. After a number of delays and further expenses in New York, most of the reasons for which he recounts in the Autobiography, Franklin finally leaves America. On route, he writes down some of his observations about shipbuilding, and he recounts his ship being chased by French warships. After doing some brief sightseeing in the English countryside, he eventually arrives in London on July 27, 1757, thus ending Part Three.
The very short Part Four explains briefly the events of Franklin's London visit and important happenings of 1757. Franklin meets some of his old English friends briefly, but his diplomacy is not entirely successful. He is told by the President of the King's Privy Council that "The King is the legislator of the colonies," and as a result is not interested in Franklin's attempts to press colonial legislation rights. Franklin argues for the importance of the colonial Assemblies and their ability to create laws, but his arguments go largely unheeded. Franklin feels that he is treated rudely in meetings, and he grows resentful towards the English diplomats. He is forced to represent and defend American taxation codes in English court, and comes close to achieving a compromise. Upon his return to Philadelphia in 1762, the Assembly takes a vote of thanks to Franklin for his efforts to promote colonial interests in Britain. Franklin then ceases writing the Autobiography, and dies two years later before he had time to finish it.
The later parts of Part Three and most of Part Four are of little interest to modern audiences who no longer study the specifics of the French and Indian War in great detail. Nevertheless, the sections are valuable for establishing Franklin's reputation as a great diplomat and for depicting Franklin as a world-renowned scholar. Franklin's appointment to press colonial rights in England reminds us that Franklin was really known more as a scientist than anything else up until the Revolution, a fact that is often forgotten today.
The foreshadowing of Part Four seems to indicate that Franklin was indeed interested in finishing the Autobiography. His mention of the English arrogance and unwillingness to compromise, as well as the sudden renewal of English interest in the American colonies after decades of "benevolent neglect," foreshadows the ensuing conflict between Britain and America. After all, it was England's sudden decision in 1763 after the Seven Years' War to reap more benefits from American colonies that largely precipitated the Revolution. Franklin would of course go on to be a major opponent of the Stamp Act and the Townsend Duty Acts, both of which he perceived to be typical cases of English imposing duties on colonists with no political representation or recourse.
The division between Part Three and Part Four is tenuous, and some editions of the Autobiography have omitted the break altogether. The edition of 1818 ended with the line, "We arrived in London..." However, it was not until some of Franklin's notes were recovered as late as 1868 that editor John Bigelow pieced Part Four onto the end of Part Three, thus extending the Autobiography's length by three pages or so.