food production due to the presence of deaths. Travel and further career In 1799, Malthus made a European tour with William Otter, a close college friend, travelling part of the way with Edward Daniel Clarke and John Marten Cripps, visiting Germany, Scandinavia and Russia. Malthus used the trip to gather population data. Otter later wrote a Memoir of Malthus for the second (1836) edition of his Principles of Political Economy. During the Peace of Amiens of 1802 he travelled to France and Switzerland, in a party that included his relation and future wife Harriet. In 1803, he became rector of Walesby, Lincolnshire. In 1805, Malthus became Professor of History and Political Economy at the East India Company College in Hertfordshire. His students affectionately referred to him as "Pop", "Population", or "web-toe" Malthus. Near the end of 1817, the proposed appointment of Graves Champney Haughton to the college was made a pretext by Randle Jackson and Joseph Hume to launch an attempt to close it down. Malthus wrote a pamphlet defending the college, which was reprieved by the East India Company within the same year, 1817. In 1818, Malthus became a Fellow of the Royal Society. Malthus–Ricardo debate on political economy During the 1820s, there took place a setpiece intellectual discussion among the exponents of political economy, often called the Malthus–Ricardo debate after its leading figures, Malthus and theorist of free trade David Ricardo, both of whom had written books with the title Principles of Political Economy. Under examination were the nature and methods of political economy itself, while it was simultaneously under attack from others. The roots of the debate were in the previous decade. In The Nature of Rent (1815), Malthus had dealt with economic rent, a major concept in classical economics. Ricardo defined a theory of rent in his Principles of Political Economy and Taxation (1817): he regarded rent as value in excess of real production—something caused by ownership rather than by free trade. Rent therefore represented a kind of negative money that landlords could pull out of the production of the land, by means of its scarcity. Contrary to this concept, Malthus proposed rent to be a kind of economic surplus. The debate developed over the economic concept of a general glut, and the possibility of failure of Say's Law. Malthus laid importance on economic development and the persistence of disequilibrium. The context was the post-war depression;