1675-1726 Guillaume de L'Isle's father had studied geography with Nicholas Sanson, and Guillaume himself studied under Jean Dominique Cassini. Cassini's severe scientific discipline instilled in de L'isle a distrust of 'authorities' and a passion for astronomical and mathematical testing of all theory. This new approach to map making is now known as 'theoretical' cartography. He was successful by the time he was 26-in 1702- in winning a place in the Academie. Between 1700 and his death in 1726, Guillauem published approximately 60 maps. After his death, de L'isle's son in law Phillipe Buache took over the works until the 1770's. Despite publishing the precise, accurate maps of his late father-in-law, Phillipe Buache was also responsible for some of the most bizarre and fanciful cartographic outlines ever published.