日落，索姆河畔圣瓦莱里

Boudin was 66 when he painted this, and by then he had a fixed working year. Summers on the Channel coast painting outdoors, winters in the Paris studio finishing what he had brought back. Around 1890 and 1891 he kept returning to one stretch of it, the bay of the Somme and the small port of Saint-Valery at its mouth. He painted the harbour there, the canal, the river, the moon coming up over the water.

That bay is enormous and almost entirely tidal. Twice a day the sea withdraws for kilometres and leaves sand, mud and shifting channels behind, which is why a canal had to be cut through to keep the port reachable by ship at all. A very low horizon and a great deal of sky is what the light there has to work with.

The canvas hangs up the coast in the castle museum at Boulogne-sur-Mer, which received it with the collection of a local donor, Charles Lebeau.