Stultifying – now there is a word we do not hear very often but it is the effect a hot July day might have on you, down by the river, just passing the time away unenthusiastically. My friend Geoffrey Smith uses it when describing my choice of painting of the month for July. In a delightful pocket book called The 100 Best Paintings in London, published by Chastleton in 2005, he describes quite beautifully the best of London’s public gallery art.

The Bathers at Asnières was painted by George-Pierre Seurat in 1884. It Is massive, weighing in at 201cm x 300 cm and fills one wall of the post-impressionist room in the National Gallery London. I can stand in front of it bewitched for ages.

The Salon in Paris, originally rejected the painting in 1884 because it was too large to feature ordinary people in a genre setting. The academy insisted large paintings were dedicated only for history or mythology. Instead it appeared first in public view at the rival ‘artists’ Salon des Indèpendants. Even then it was not sold but eventually was acquired by the art critic Fèlix Fénéon, and somehow found its way via the Tate collection to the National Gallery.

Seurat was of one of the promoters of pointillism (painting with colour dots) although this painting predated that innovation. What this painting does reveal though is the artist’s interest in the theory of colour and how tricks can be played on the eye. Note the boy sitting on the bank, how the water is light against his dark back yet dark against his sunlit arm. Seurat is playing with emphases of shadow and colour.

Revolution and the subversive avant garde inform the story behind the painting, as one of changing the guard from the rich bourgeoisie, seen being ferried from La Grand Jatte, a pleasure Island in the Seine, and the working socialist class seen enjoying a holiday break by the river. The factories and the railway in the distance mark the march of industry in the late nineteenth century. It was the railway that brought the Parisian artists out to Asnières, Renoir and Manet also producing paintings from this Suburban stretch of river.

July may yet provide some stultifying hot days for us to enjoy. If it does do find a river to sit by and simply pass the hours away.