REFORMATION OF CARTOGRAPHY IN FRANCE 137 



perspective drawings; as the science of surveying developed, 

 efforts were made to represent the actual area occupied by a 

 range. This, combined with the profile, produced a three- 

 dimensional effect. 



One of the more successful methods of rendering relief was 

 evolved by the Swiss cartographer, Hans Konrad Gyger 

 (1599-1674).^ In his maps of the Swiss cantons he attempted 

 to show the land surface as though viewed from above, work- 

 ing in the folds and hollows by careful shading and leaving the 

 higher areas untouched. His skilful workmanship, combined 

 with his extensive personal knowledge of the country, produced 

 a remarkably plastic effect, though he could convey only relative, 

 not absolute, differences in altitude. That his method does not 

 appear to have been generally followed was no doubt due to 

 the lack of adequate data. For the next century at least the 

 representation of relief was generally confined to shading valley 

 slopes at a more or less uniform distance from the rivers. This 

 style is employed, for instance, in the map of the environs 

 of Paris made by members of the Academy of Sciences and 

 engraved by La Pointe in 1678. Even on the sheets of the 

 Cassini survey, seventy years later, no essential advance had 

 been made, and the effect is much inferior to that achieved by 

 Gyger. 



The method of hachuring, by which relief is indicated by 

 lines (hachures) running down the direction of greatest slope, 

 may have been a development of this practice. The principle 

 was fully worked out in the course of the eighteenth century to 

 meet the requirements of military commanders. J. G. Lehman, 

 on the analogy of the shadows thrown by an overhead light, 

 propounded the theory that the greater the inclination of 

 the surface to the horizon the heavier should be the hachuring, 

 and he worked out a systematic scale for the thickness of the 

 strokes. Hachuring, however, has several defects; if carried out 

 elaborately, the heavy shading obscures much of the other 

 detail on the map, and by itself can give no absolute value for 

 the difference in elevation between one point and another. 

 Moreover, without reference to other features, it is diflicult 

 to distinguish elevations from depressions. 



^See Weiss, L., Die Schweiz auf alten Karten, 1945, pp. 107-66. 



