Georges Seurat, 'The Channel of Gravelines, Grand Fort-Philippe', 1890

In the years immediately prior to his early death in March 1891, aged just 31, Seurat spent several summers on the Channel coast, producing more than 20 paintings of its harbours and marine views. This is one of four paintings he made in 1890 near the town of Gravelines, a small port on the northern French coast between Calais and Dunkirk. Unlike Monet, who was attracted to the area’s dramatic cliffs and wild seas, Seurat chose more subdued locations that, typically, included man-made structures such as harbour walls, jetties, buildings, masts and poles, which provided verticals and horizontals with which he could contain and frame the landscape.

This is one of Seurat’s most reduced and spare compositions. Positioned on the sand dunes of Petit-Fort-Philippe, we see the shore in the morning light after the receding tide has left a broad expanse of open beach in the foreground. On the other side of a narrow channel is a semaphore flying signals warning that the harbour waters are too shallow for boats. Along the seawall, there is a single row of low buildings. The scene appears almost deserted, apart from some distant figures.

Using the horizontal blue stripe of the channel and the seawalls, Seurat divides the painting into two near-equal halves of sky and sand. The vertical lines of the masts and signal tower are echoed just below by two mooring posts, which subtly connect these two halves like staples or hinges. Seurat skilfully avoids making the scene too static by slightly elevating the horizontal axis as our eye follows it across from left to right. This also helps create an effect of depth into an otherwise flat picture space. The solitary mooring post at the painting’s right edge provides a point of focus that anchors the composition. The horizontal strip of blue that bisects the canvas is offset by a diagonal band of white on the beach below. Seurat places this white band parallel to the edge of a triangular patch of green grass in the lower left corner. The triangle was a shape Seurat often used but, in this instance, contemporary photographs show there was a grassy verge along the sand dunes. Its inclusion in the painting, along with other features – such as one of the houses that still survives – confirms Seurat’s art was based on direct observation.

Two areas of carefully modulated colour dominate the painting: the pale golden-yellow of the beach and the light blue of the sky. However, these are far from being flat areas of unvaried colour. Closer viewing reveals Seurat’s pointillist technique as he covers the canvas with a shimmering mosaic of dots and strokes of unblended paint to create subtle gradations of luminous tone. Although highly controlled, these brushstrokes are not uniformly applied, but range from tiny dabs of colour to relatively broad strokes.

Seurat has also added a painted border of coloured dots to the painting, which creates a transition between the image and the actual frame. Each section has been calibrated to the adjacent area of the picture to intensify that area’s chromatic impact – for example, the deep indigo near the bottom complements the yellow sand, but Seurat adds red dots at the bottom left corner where the border is next to the green. Above the sky, the frame is predominantly orange.