The map highlights an interesting demographic period after the abolition of slavery in Britain (1838) and France (1848), creating a dearth of workers in European colonies. The black lines coming out of Congo to Mauritius and La Reunion show the passage of workers from Africa to work on the sugar plantations owned by the French. The brown lines show the influx of indentured labourers from French settlements in Tamil Nadu in India, to fill the void created by the end of slavery. A substantial number of African and Indian migrants also make their way to the West Indies. The small blue line across the Mediterranean shows French migration to Algeria, one of its richest colonies.

The thick green lines dominating the map show the huge wave of immigration from Britain to America, Canada and Australia; Australia became particularly attractive to prospective settlers after gold was found there. The number of British emigrants to America, however, was dwarfed by the number of Germans; in the period 1840-80, they made up the largest percentage of American immigrants. Migration was motivated by economic prospects and after the 1848 revolutions in some German states, there was also a wave of political refugees fleeing to North America. Brazil gained independence from Portugal in 1822, but immigration there from Portugal actually increased after it stopped being a colony, mainly peasants from rural areas. There was also a substantial minority of immigrants from Germany, to the point that Prussia banned immigration to Brazil in 1859 after reports of ill treatment on coffee plantations

China became an important source of labour in the mid-eighteenth century. The southern areas of the country suffered from political and economic instability, thanks to the weakness of the ruling Qing dynasty and the ongoing Opium Wars with the British. Chinese immigration to Cuba began in 1847 after the abolition of slavery; the Spanish replaced African slaves with Chinese indentured labour. Similarly, Chinese workers were often shipped under contract by agents to California during the Gold Rush, where they faced harsh working conditions and routine violence. The Chinese population in Australia, also spurred by the Gold Rush, grew large enough for the government to initiate anti-Chinese legislation.

Copies are held at ENPC: 3384/C161; LC: G3201.E27 1858.M5 TIL (989687134/MAPS).

Charles Joseph Minard (1781-1870) was "a true pioneer in thematic cartography and in statistical graphics" (Friendly). After completing his studies at the École des Ponts et Chaussées, (the School of Bridges and Roads) he began work as a civil engineer. The beginning of his career coincided with the beginning of the Napoleonic Wars, and he headed a project to repair the wet dock at Flessingue after it was destroyed by the British. He was then posted to Antwerp to oversee a project there and was caught in the siege of Antwerp in 1814, an experience that affected him greatly. He was named Superintendent of his alma mater in 1830. Six years later, he became Inspector of the Corps of Bridges. In 1851, he took mandatory retirement, although still working for the school in an advisory capacity, and undertook private research. This is when his cartographical career began in earnest.

Minard's genius lay in his realisation that maps could provide visually clear renditions of complicated statistics. He wrote that the aim of his work was not to convey statistical results, but to show the relations between them, which would otherwise have to be worked out by the reader. He would often alter geographical reality on a map in order to make a diagram clearer, and so added the term 'approximative' to the title of his works to explain his decision. He was possibly the first to use the flow-map technique (his writing indicates that he believed he had invented it) and he was certainly the first to use pie charts on a map. His work was "a combination of cartographic ingenuity and concern with the graphic portrayal of statistical data that was almost unique during the central portion of the century" (Robinson).

The importance of Minard's work was quickly recognised by the French government. He was awarded the Legion d'Honneur, and throughout the 1850s all Ministers of Public Works in France had their portrait painted with a Minard chart in the background. In 1861, his work was presented to Napoleon III. Minard's maps were not widely known in his lifetime outside of the intelligentsia and upper levels of government, suggesting that he published them privately (Robinson).

Minard continued to write and create maps in retirement, until the onset of the Franco-Prussian War. In 1870 Minard heard that the Prussians were marching on Paris. Determined to avoid a siege like the one he had suffered under in Antwerp 56 years before, he left for Bordeaux. The journey was too much for him, and he died six weeks later.