A rare separately published map, made by a Royal geographic engineer Jean-Louis Dupain-Triel was published on the eve on the French Revolution and represents the hydrological structure and mountain ranges of France.
Although the image appears to copy Philippe Buache’s older map Carte physique ou géographie naturelle de la France, first published in 1744, this map is corrected and most notably includes pioneering new methods of representing the geographic data with contours.
Marcellin Du Carla-Bonifas’s “language of elevation” and Jean-Louis Dupain-Triel
In 1782, Jean-Louis Dupain-Triel bought an unpublished work on map-making titled Expressiondes nivellements (Expression of Leveling) by a Languedocian geographer Marcellin Du Carla-Bonifas and published it in 600 examples, giving 150 examples to the author and keeping the rest for himself to resell.
Marcellin Du Carla-Bonifas, who was ahead of his time, did not follow the established methods to represent the hydrography and elevation. He started measuring the elevation of land at the sea level, what was at the time unusual for the military engineers. As Du Carla-Bonifas understood, that the sea level is arbitrary, he wanted to establish the average, by measuring the sea levels at the mouths of the rivers.
Another one of his inventions in cartography was thickening every tenth contour line on the map, to make it clearer to read, calling the contours “the language of elevation”. Du Carla-Bonifas generally believed one could add information on the map, without overcrowding it with printed data. He especially believed in clear contours, which would enable the reader to recognize the data instantly.
After publishing Marcellin Du Carla-Bonifas’s work on leveling, Jean-Louis Dupain-Triel copied Du Carla-Bonifas’s ideas and published this map on hydrology of France. In the following years he continued publishing maps with more and more detailed and strong contour lines, with a hope, that the new government after the French Revolution would adopt his ideas. (Josef Konvitz, Cartography in France, 1660-1848: Science, Engineering, and Statecraft, 1987, pp. 77,78).
Today the Dupain-Triel’s maps are considered as curiosities in the elevation data visualisation.
Worldcat does not list any examples. We could find examples in the Basel – Bern library database and at the list of maps at the Harvard library.
References: Josef Konvitz, Cartography in France, 1660-1848: Science, Engineering, and Statecraft, 1987, pp. 77,78.