the wind to move upstream. Several specialized businesses maintained this system transport. Workers known as nautes had a monopoly of transport on large rivers and used boats, whereas the operated on the small rivers and in the marshes using rafts floating on inflated goatskins. There were two groups of utriculari, one in Sisteron and one in Riez. This trade fed the activity of an important port, near to the crossroads at Sisteron, at the place called 'Le Bourguet'. In the vicinity of L'Escale a port existed before the Roman conquest, but was developed during the 1st century BC, and was prosperous until the Crisis of the 3rd Century, before recovering its economic activity until the beginning of the 5th century. Middle Ages In the Middle Ages, the county of Forcalquier stretched all along the Durance, from Cavaillon to La Roche-de-Rame, close to Embrun. From the 12th to the 19th century, the river was used for floating timber downstream, in particular by the monks of , who were given the privilege in 1191 to use the river.) The timber was used in the towns of the southern plains and in the shipyards. Other goods were transported by the river, including salt, those these were subject to ten tolls along the of the river. The bridge of Sisteron, erected in the Middle Ages remained until the middle of the 19th century, the only crossing between two firm banks along the Durance. After the year 1000, the number of ferries increased, including some Cable ferries plied between the two banks of the main channel. The oldest known one was the one between La Roque-d'Anthéron and Cadenet (in Gontard), recorded in 1037. This ferry at Cadenet and one at Mirabeau were used to transport flocks of sheep for seasonal migrations. Thereafter, there is evidence of ferries at many other places notably Rognonas, La Brillanne (13th century), Noves, Orgon, Le Puy-Sainte-Réparade, Meyrargues, Pertuis, Peyrolles, that of Cante-Perdrix in Mirabeau, Manosque, Giropey, Château-Arnoux, Le Bourguet, Volonne, . Other ferries were established to supply the windmills built at the end of the 18th century in , Upaix and Claret. Nevertheless, the ferry services were scarcer than on the Rhône with a ferry every on average, versus every on the Rhône. Starting from the 12th century, wood bridges were also built. They lasted varying times until they were destroyed in various ways: at Maupas (now Pont de Bonpas