By 1848 the French had abolished slavery in all their possessions. The Dutch did not do so till 1863; in which year also the status of slavery ceased in the United States. Slavery lingered in some of the South American states until 1840-5. In the Portuguese African possessions slavery was abolished in 1878 and in Spanish Cuba and Porto Rico in 1886; while Brazil remained a slave-holding country until 1888, the final and somewhat abrupt abolition of slavery being one of the causes which led to the downfall of the Emperor. However, long after British or French possessions had ceased to offer inducements to the slave trader to run illegal cargoes, there were sufficient countries in the Western Hemisphere to provide an excellent market for negroes, while the Muhammadan world in the East continued to make greater demands than ever on the Central African slave preserves[105]. To counteract the attempts to evade the law a powerful British squadron swept the West coast of Africa; but in spite of British efforts to intercept slave-trading vessels, these latter continued to run cargoes across to the United States, Cuba and Brazil, and it was not possible for this traffic to be wholly vanquished until the abolition of slavery in those countries closed the last markets to the slave trader. A most interesting light is thrown on the vastness of the area covered by these slave-trading operations in a work by the Rev. S. W. Koelle (a missionary of the Church Missionary Society) published in 1854, entitled “Polyglotta Africana.” Mr Koelle established himself at Sierra Leone for some years and busied himself in collecting from the slaves who were landed there from British cruisers vocabularies of the languages they spoke in their own homes. In this way he took down over 200 languages, which represented most of the tongues of the West coast of Africa, of the upper Niger, of Senegal, of Lake Chad, the South-west African coast as far as Benguela, Nyasaland, the Zambezi delta and the South-east coast of Africa, and even Wadai.