Gian Domenico Cassini as Hydraulic Consultant in “Water’s Affairs” about the river Reno

Gian Domenico Cassini is still nowadays famous for his activity as astronomer, but in the first years of his professional career, he was successfully involved in another important scientific activity. Since 1657 Cassini was appointed hydraulic consultant in “water’s affairs” (ne' negotii dell'acque) for the city of Bologna and he took part in the centuries‐old debate concerning the regulation of the River Reno between the provinces of Bologna and Ferrara. On this role he took part in several visits to the waters that concerned the study of the lower course of the Po and the Reno. Between the fifties and the sixties of the 17th century Cassini was the leading actor of the Bolognese delegation. He studied the history of the rivers Po and Reno, carrying out many experiments with flowing water canals and wrote many hydraulic papers about the river Reno. In 1660 he took part in a visit to the waters between the provinces of Bologna and Ferrara, chaired by Cardinal Borromeo and in the conferences in Rome promoted by the Holy Congregation of Waters. The result of the visit was summarized by Cassini in the "Report about the violent state of the Bolognese waters and the easiest way to return them to their natural state" (Relazione dello Stato violento dell’acque deBolognese, e del modo più facile per ridurle allo stato naturale). In 1669 Cassini resigned from the position of hydraulic consultant to move to Paris. In this article we provide an overview of the hydraulic side of Cassini’s personality and we discuss the peculiarity of the typically Italian figure of the hydraulic consultant between the 17th and the 18th century.