English: This depiction of a lock on the river Oise is one of four such compositions inspired by the area of Pontoise, a village north of Paris. Pissarro moved to Pontoise after he returned from England following the Franco-Prussian War (1870-71). The ten years he stayed there were not only his most prolific, but also saw the height of his artistic talents. It was also in Pontoise that Pissarro worked with Edgar Degas (1834-1917), Mary Cassatt (1845-1926), and Paul Cézanne (1839-1906). Pissarro's influence on Cézanne was especially important, as Pissarro encouraged him to paint en plein air, or outdoors. As a painter, Pissarro pursued many of the same goals as the Impressionists and exhibited with them from 1874 onward. However, the group is far from being unified stylistically, and there were many differences among its members. In contrast to other Impressionists, Pissarro was interested in darker tonalities, especially blues, greens, and browns. The more sober colors of his paintings suggest his debt to the earlier French artist Gustave Courbet (1819-1877).