Both the beauty and interest of fractures and fracture networks are easy to grasp, since they are abundant in nature. An example is the road from Digne to Nice in the south of France, with an impressive number and variety of such structures: the road for the most part, goes through narrow valleys with fast running streams penetrating the rock faces; erosion is favored by the Mediterranean climate, so that rocks are barely covered by meager vegetation. In this inhospitable and sterile landscape, the visitor can im- mediately discover innumerable fractures in great masses which have been...