1824 pencil and ink drawing showing the old French factory at Patna on the Ganges. The Dutch, French, British and Danish East India companies all had factories at Patna, the center of opium and saltpetre trade in northern India. France was not able to take back its factory at Patna when it recovered its Indian settlements (Pondicherry, Chandernagore, etc.) in 1816 following the Treaty of Paris of 1814. Cropped from the original drawing by Sir Charles D'Oyly (1781-1845) dated 1824.