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Interactive Visualization: Letters in Voltaire’s Network

Dan Edelstein , August 2016

The data visualizations below were created using the Palladio application developed at Stanford. The embedded visualizations are Palladio Bricks. Palladio is freely available to use at and the source code is available on GitHub here.

You will find an explanation of the visualization at the bottom of the page.


There are four visualization elements to be found on this page. All the metadata for Voltaire’s correspondence comes from the Electronic Enlightenment Project at Oxford University (subscription required). The visualization elements were produced using Palladio, a suite of data visualization tools created at Stanford University.

  1. On top, visitors will find a map of Voltaire’s correspondence. The data on the point to point map show source and destination location. The point size reflects the total number of letters sent/received at a place. We were only able to map letters with location metadata, meaning that close to 7,000 letters (a little over one third) do not feature on this map at all. The map is interactive: hovering with the mouse over a point will reveal the number of letters to and from that place; hovering over a line will reveal the number of letters from one place to another. (NB: remember that these numbers only reflect letters with location metadata).

  2. Below the map is a timeline, which can be used to filter the letters displayed on the map according to the chronological selections. The timeline shows the number of letters exchanged per year (source data: “letter year”). The letters in each bar are grouped by nationality of sender or recipient (i.e., whomever Voltaire was writing to, or receiving a letter from). Hovering over the different sections of the bar will illuminate all letters by that nationality. Since the temporal metadata is almost entirely complete, all of the extant letters in Voltaire’s correspondence are represented here.

  3. Below the histogram is a facet filter. The count is based on the number of letters and the dimensions displayed are “Nationality,” “Source,” “Destination,” “Gender Group,” “Correspondent Role.” This viewer allows you to filter both the timeline and the map according to one or multiple values across one or multiple dimensions. For instance, by selecting “English,” “Scottish,” “Irish,” and “Welsh,” you can identify all of Voltaire’s British correspondents; or you can select “German” and “female” to identify the 16 German women with whom Voltaire corresponded.

  4. The names and letters associated with any group of individuals selected in this way appear below the histogram, in a table. The list is based on “EE URI.” Additional columns include “Full Name Reversed,” “Nationality,” “Source,” “Destination.” The hot links on the left-hand side will take you to the Electronic Enlightenment page containing a transcription of this particular letter.

See the project Schema page for data viewer, the data schema, and a link to the data files.

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Cite as

Dan Edelstein. Interactive Visualization for Voltaire’s Correspondence Network. Letters in Voltaire’s Network [Created using Palladio,].