Roger Congratulations for visiting France and discovering the wide variety of its sundials. As for the Tonnerre analemma, it is not the work of Lalande, but of three people, Dom Férouillat, Guémadeuc and Daret. It was begun in 1786 and has a long and chaotic history all along the 19th century. A very interesting book dealing with this analemma was recently published by A. Gotteland, B. Taillez and G. Camus (from the Société Astronomique de France) : "La Méridienne de l'Hopital de Tonnerre". It gives all the historic, technical and gnomonic details .As far as I know it can still be available (about 25$) at the :
Centre Hospitalier de Tonnerre BP 127 89700 TONNERRE France Best regards Jean-Paul Cornec WGS 84 (without SA) 48° 44' 20" N 03° 27' 32" W
