The Tugboat, Canal in Samois

By 1901 the method was almost 20 years old. Signac and his friend Seurat had worked out Neo-Impressionism in the mid-1880s, laying pure colours side by side in separate touches so the eye, not the brush, does the mixing. Seurat had been dead ten years by now, and Signac kept the technique going, larger and looser. Here a steam tug pushes along the canal at Samois, a village on the Seine near the Fontainebleau forest. Signac loved boats and spent much of his life on the water, and he was glad to put a smoking modern tugboat at the centre of a picture about light. Each stroke sits in its own small square of colour, with a rim of pale canvas around it that makes the whole surface flicker.