While the mountain pictographs of the Homann map rely on an outline in combination with shade-lines on the southeastern slopes (implying high-oblique, northwest illumination), the mountain forms of the Dunn map are rendered by hachures (slope lines) on multiple sides.
(22) Two developments were crucial: indirectly, the invention of the contour line (curved lines of equivalent elevation first used to show the overall form of landmasses on a French map of (1791) and, directly, Johann Georg Lehmann's 1799 invention of shadow-hachures, an arrangement of hachures that emphasized the "transition from level ground to steep gradients." Simply put, Lehmann subjected previously impressionistic slope hachures to a dual system of arrangement; in a section of slope, hachures seem to end on an implied line of consistent vertical height (like a contour line), and vary in thickness according to steepness of slope.
This "Paris seen in hachures
," as Kafka called it, was an attempt to fragment the impressions of things, in accordance with the facts.
La touche y est virevoltante, generant empreintes, hachures
, courbes, semi courbes et entrelacs.
I anticipated commentary on the mixture of point, line and area symbols, on the selection of colours and hachures
that mimic perceptions, on the evolution of choropleths and other thematic techniques, and even on the origins of the idea of making interpretive statements about collective social behaviour in mapped form.
It gives no indication of elevation by contours or spot heights, while hachures
are used only to show extreme situations such as the steep drop below Pope's Hill at the northern end of Monash Valley.
It is the Federal Territory Feature Map, sheet 7, drawn ca.1915, in a version with hachures
held in the Dickson offices of the ACT Planning and Land Authority.
The presentation of the maps harks back to the original printed maps of the period, with their distinctive watercolour-like tones, hachures
and lettering, and their fascinating historical and geological information.