The early quantification of the catchment water balance in the 17 ^th century has been well documented. But there is one book, called L’Hydrographe or La Science des Eaux, that was published by a Jesuit priest, Père Jean François, in Rennes in 1653 (20 years before the publication of Pierre Perrault’s De l’Origine des Fontaines) that has been largely overlooked. The book is split into four parts that deal with the formation, movement and mixing of waters and the origin of springs. Further parts were published with La Science des Eaux that deal with the arts of surveying and drawing of maps, and the construction of canals and fountains, with a final part on doing arithmetic with integers and real numbers “with pen and counters.” François was convinced, much more than Perrault, that the waters of springs were the result of rainfall and snowmelt.