Isochronic Passage Chart for Travellers

A splashy, yet practical, one-look travel guide

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In the early 1880’s mapmaker Francis Galton (best known today for his unfortunate work in eugenics) began to imagine a series of ideal trips.* Each started in his home city, London, but from there they ranged far afield—to Greenland, or Morocco, or the distant reaches of the Pacific. By figuring out how long each of these trips would take, and drawing lines grouping those destinations that could be reached in an equal amount of time, he figured he could provide a service to travelers, sailors, and those who simply wanted to know how long it would take their mail to get someplace.

Galton’s calculations presumed smooth sailing all the way: “I assume the seasons to be favorable, that immunity has been obtained from political obstructions, and that friends on the spot have made preparations to avoid delay,” he wrote. For each trip, he consulted steamer timetables, estimated package-shipping times, and personal correspondence from friends at the Post Office. He then sorted the destinations into different color groupings—everywhere one could get to between ten and 20 days was yellow, for example, while everything that took more than 40 days to reach was brown.

When he was done, he’d come up with a splashy yet practical one-look travel guide: the first example of what he called an “Isochronic Passage Chart.”

At the time Galton released his map, isotherms and isobars—lines that group areas exhibiting equal temperature or atmospheric pressure—were already a well-established part of weather mapping. The applications of Galton’s concept to travel and postal delivery times caught on quickly. Mapmakers across Europe began coming out with their own isochrone maps, based in different cities and pitched at different scales. ~ Atlas Obscura

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Title: Isochronic Passage chart for Travellers

Subtitle: "Showing the shortest number of days journey from London by the quickest through routes and using such further conveyances as are available without unreasonable cost. It is supposed that local preparations have been made and that other circumstances are favourable."

Author(s): Galton, Francis, 1822-1911

Publisher: London : Edward Stanford, 1881.

Archive: Princeton University Library G3201.P1 1881 .R6