Figure 2.

The potentiometric map (named “hydrographic map”) of the Hesbaye aquifer as drawn by Gustave Dumont in his report, dated February 10, 1856 (Dumont 1856). As mentioned in French in the legend (lower left of the figure), the contours are “the intersection between the underground water surface with horizontal planes.” The red lines central in the map are the proposed excavations in the chalk for an aqueduct from “Ans” to “Lantin” (about 5 km in length) and two connected water supply galleries.