The results of these investigations procured for him the friendship of Sir Joseph Banks, the President of the Royal Society, and Thompson was not the man to lose opportunities for want of making use of them. In 1779 he was elected a Fellow of the Royal Society, "as a gentleman well versed in natural knowledge and many branches of polite learning." In the same year he went for a cruise in the _Victory_ with Sir Charles Hardy, in order to pursue his experiments on gunpowder with heavy guns. Here he studied the principles of naval artillery, and devised a new code of marine signals. In 1780 he was made Under-Secretary of State for the Northern Department, and in that capacity had the oversight of the transport and commissariat arrangements for the British forces. On the defeat of Cornwallis, Lord George Germaine and his department had to bear the brunt of Parliamentary dissatisfaction. Lord George resigned his position in the Government, and was created Viscount Sackville. He had, however, previously conferred on Thompson a commission as lieutenant-colonel in the British army, and Thompson, probably foreseeing the outcome of events and its effect on the Ministry, was already in America when Lord George resigned. He had intended landing at New York, but contrary winds drove him to Charlestown. It is needless to trace the sad events which preceded the end of the war. It was to be expected that many bitter statements would be made by his countrymen respecting Thompson's own actions as colonel commanding a British garrison, for at length he succeeded in reaching Long Island, and taking the command of the King's American Dragoons, who were there awaiting him. The spirit of war always acts injuriously on those exposed to its influence, and Lieutenant-Colonel Thompson in Long Island was doubtless a very different man from that which we find him to have been before and after; nor were the months so spent very fruitful in scientific work. In 1783, before the final disbanding of the British forces, Thompson returned to England, and was promoted to the rank of colonel, with half-pay for the rest of his life. Still anxious for military service, he obtained permission to travel on the Continent, in hopes of serving in the Austrian army against the Turks. He took with him three English horses, which rendered themselves very objectionable to his fellow-travellers while crossing the Channel in a small boat. Thompson went to Strasbourg, where he attracted the attention of the Prince Maximilian, then Field-Marshal of France, but afterwards Elector of Bavaria. On leaving Strasbourg, the prince gave him an introduction to his uncle, the Elector of Bavaria. He stayed some days at Munich, but on reaching Vienna learned that the war against the Turks would not be carried on, so he returned to Munich, and thence to England. M. Pictet gives the following as Rumford's account of the manner in which he was cured of his passion for war:--