Jean-Charles Houzeau and his relief map of Europe (1857) presented by contour lines

Abstract

The relief map of Europe by contour lines (hypsometrical curves) in a 1:5,000,000 scale is a monumental work produced by J.-C. Houzeau when he published his “Histoire du sol de l’Europe” (1857).This hypsometrical map of Europe is a genuine masterpiece: contour lines on the recently discovered minute-maps, worked out in a 1:1,000,000 scale, were reduced to a smaller 1:5,000,000 scale, with the aid of a pantograph. This work by J.-C. Houzeau, carried out with the help of his brother Auguste, is a breathtaking achievement from a scientific and geographic point of view. J.-C. Houzeau made use of tens of thousands of altitudes obtained from the engineers-surveyors of the “Ponts et Chaussees” {roads and bridges), civil servants (if any) in the various countries concerned and the engineers-geographers of the military services, in charge of laying out in the Ordnance Survey Maps. More particulary, he used more than 12,000 barometrical marks! All the points that were used are positioned (in a 1:1,000,000 scale), in latitude and longitude, in one single frame which he created (conical projection with the Paris meridian as origin), involving thus an important number of conversions (the standard of the Greenwich meridian had not yet been established).