Sankey diagrams are a type of network flow map. They depict the rate of flow of an element (people, products, energy) across space or time, through processes, or between conceptual categories. Rather than singular nodes for discrete elements, their main features are bands or arrows showing the direction of flow and the changing volume (or amount) of the diagram’s elements. The width of the bands or arrows is proportional to the flow rate of the elements.
Charles Joseph Minard (1781–1870). Carte figurative des pertes successives en hommes de l'armée française dans la Campagne de Russie 1812-13. Cheshire, CT: Graphics Press, 1990 [reprint].
In 1869, Charles Minard created this famous map of Napoleon’s invasion of Russia in 1812 ( translated version below). The thick band shows the size of Napoleon’s army during their advance, (in beige) and in its retreat (in black). The width of the band is proportional to the number of soldiers in the army at each point; each millimetre represents ten thousand men. The loss of life looms in the thinning of the bands. The temperature during the retreat is shown on the line graph at the bottom. The effect of temperature on the outcome of the battles emerges easily from Minard’s design. This map was heralded as ‘probably the best statistical graphic ever drawn’. In viewing this exhibition, do you agree?
Charles Joseph Minard, Carte figurative des pertes successives en hommes de l’armée française dans la Campagne de Russie 1812–13, 1869, diagram, Europeana —Bibliothèque nationale de France, accessed March 15, 2023, https://www .europeana.eu/item/9200517/ark__12148_btv1b52504201x.
Sebastian C. Adams (1825–1898). A Chronological Chart of Ancient, Modern and Biblical History. Chicago: J. Andrews, 1878.
This Adams Synchronological Chart, first published in 1871, was printed on a giant scroll. It is a set of timelines beginning with the Christian Bible that later merge into historical material. Biblical genealogical timelines are on the top half of this infographic. An early version of a Sankey diagram showing the rise, merging, and fall of nations from ancient civilizations makes up the bottom half. The long snaking bands represent nations and their relative sizes and strengths. Adams’ chart lends credence to biblical events by employing the scientific aesthetic of the time and combining both biblical and historical events in one diagram. It claims authority by association.
Willard C. Brinton (1880–1939). Graphic Presentation. New York: Brinton Associates, 1939.
This is a meticulously handcrafted Sankey diagram even though it predates use of the name ‘Sankey’ by decades. In 1939, before computer-based graphics, Willard Brinton, author of the first textbook on data visualization in 1919, outlined a standardized way to make Sankey diagrams in this 1939 book. This Sankey was made by directing the paths of one thousand paper strips with pins so that the number of strips in each section corresponded to the percentage represented by each category. The strips were then photographed so that shape of the chart was smooth. The machine that created these graphs and the diagrams it created were called a ‘cosmograph’. The replacement of ‘cosmograph’ with ‘Sankey’ is a loss for the world of data visualization.
Officially, the first Venn diagram was created in 1880 by John Venn to simplify the way relationships between sets of objects were conveyed, which at the time involved long lists of relationships of sets and their elements (as in: ‘all A are in B’, ‘some C are in A’, ‘none of D are in C’). Venn’s visualization made it much easier to see these relationships. A Venn diagram is made of two or more circles that overlap to show all the possible relationships among sets of items (inclusion, exclusion and union or variations of some, all, and none). Nearly one hundred and fifty years later, it is hard to image how we would express these relationships any other way.
