La “fortezza invisibile”: il telegrafo ottico Chappe nella Francia napoleonica

Even in the defensive and fortifying processes, two aspects can be found: the material component and the immaterial one. If all the constructive, material and structural procedures are the first, for example, all that concerns remote communications (maximum optics) belongs to the second, an indispensable tool to complete an optimal strategy for offensive and/or defensive operations. Remote optical transmissions are closely connected to the management of defensive systems: this is also what happens with the optical telegraph of Claude Chappe, conceived during the French Revolution and adopted by Napoleon for the potential inherent in the strategic and territorial logic, as for the organization, structuring and sending of encrypted messages (which since the sixteenth century had also seen the interest of Leon Battista Alberti. The densest part of the network spreads to France, from Paris to the borders of the nation. In Europe, you will see achievements in Spain, up to Russia. The Lyon-Paris-Venice line also led to the construction of a Lombard-Piedmontese section. The present contribution stems from a conspicuous research, founded on the twenty-year collaboration of Marotta with the FNARH (Fédération Nationale des Associations de Recherche Historique sur la Poste et les Télécommunications).

The system included the installation in high positions (hills, towers or bell towers) of a mechanical device, which could be reached at a distance of kilometers. On top of a fixed pole of about 5 m, the apparatus consisted of a central axis (ordinateur) at the ends of which two mobile arms (indicateurs) were fixed which allowed (in the variation of the reciprocal positions and inclinations) to realize multiple signals, at the base of an entire encrypted visual alphabet, arrived  in 1841 up to 61000 messages. Multiple types of models made. The contribution will return the chronological developments of the system, in time and space of territories involved, with the relative comparisons of types, models and languages, also through 3D modeling.