Geometry as a Tool to Manage the Territory. Nicolaas Cruquius and the Map of the Merwede

In 1729 the Dutch cartographer Nicolaas Cruquius engraved a map that became a benchmark for every future illustration of a territory. The map, showing the bed of the river Merwede and its surroundings, was made to control an area subject to inundation and flooding, understand the territory, and plan projects to solve the thorny problem of water management. In this superb map, divided into two tables, Cruquius adopts contour lines of equal value. This was a first. What Cruquius did was reinterpret and reuse the isogones employed roughly thirty years earlier by another scientist to represent a physical phenomenon, and then use them in a different context. In fact, in 1701 Edmund Halley had employed isogones in a map he drew to describe magnetic declination over the ocean. Halley and Cruquius use lines of equal value to describe two very different models (one is a physical phenomenon; the other is an orographic model). However, they both helped to legitimise the use of contour lines to represent geographically-based phenomena. In 1712 Cruquius had made an accurate map of Delfland. This extremely precise map reveals contamination between zenithal projection and perspective view, both of which sometimes appear in the same table in a seamless shift from one projective mode to another. The simultaneous presence of different projective methods was inspired by sixteenth- and seventeenth-century maps. The method creates images that are accurate, measurable, and captivating at the same time, but they are a far cry from the projective integrity that cartography was to acquire during the eighteenth century. Cruquius adopts isobaths to maintain the plastic effect in a zenithal projection, but abandons them in the secondary tributaries where he uses more conventional graphics which were inspired by earlier examples and were to become quite common to portray water flowing along rivers. A similar graphic depiction of water is present in the zenithal plan of Rome by Giovanni Battista Nolli engraved just nineteen years after the Merwede map. The way in which natural elements are represented in Nolli’s map, the accurate measurements, and deliberate rejection of central or pseudo-axonometric projection, warrant a comparison between Curquius’ impressive map and the one made by Nolli.