Economic renaissance was accompanied by a corresponding increase in the population. From 4,000,000 in 1831 it rose to 5,000,000 in 1870, and to 7,500,000 in 1911. With a density of 652 persons per square mile, Belgium became the most thickly populated country in the world and only consumed a fourteenth part of her industrial production. The necessity of finding new markets abroad and of discovering some substitute for the loss of the Dutch colonies, which had proved so helpful during the period of union with Holland, might have been felt by any far-sighted statesman. Leopold I had already devoted some attention to the problem. He encouraged several Belgian settlements in Rio Nunez, where a regular protectorate was established for a short time, in Guatemala and in various parts of Brazil. None of these enterprises, however, bore fruit, and the problem was still unsolved when Leopold II ascended the throne in 1865. [_FOREIGN ENTERPRISES_] The search for a colonial outlet for the activity of the nation dominated the reign of the new king and absorbed all the energy he was able to spare from military problems. As Duke of Brabant, Leopold II had already drawn the attention of the country to the future development of China. He had formed several projects with regard to the establishment of a Belgian settlement at the mouth of the Yangtse-Kiang and on the island of Formosa. Their failure did not prevent him from taking, later on, an active part in Chinese affairs. The Imperial Government did not entertain towards Belgium the same distrust as it did towards the European Great Powers, and King Leopold several times had the opportunity of acting as intermediary between these Powers and the Chinese Government, in order to obtain concessions. He became thus, in later years, the initiator of the Peking-Hankow railway. The difficulty of finding a field of economic activity in foreign countries became, nevertheless, more and more apparent, and, without giving up his Chinese policy, the Belgian king endeavoured to ensure to his country some part of the vacant territories which had not yet been seized by other European nations. When his Congo enterprise was in full swing, he proposed to buy the Canary Islands from Spain (1898), and, after the Spanish-American War, opened negotiations with America with regard to the future development of the newly acquired Philippines. He was also concerned, for a time, with Korean, Manchurian and Mongolian enterprises, and nothing but the progress of the Congo scheme put a stop to his incessant search for new opportunities.