Spot on

Art - Tom Rosenthal puts the second-division divisionist back in the picture

London, having missed out on the great Signac retrospective in Paris (it's now at the Van Gogh Museum in Amsterdam until 9 September, and well worth a visit), must make do with a much smaller, but still distinguished show, also from Paris, at the Courtauld Galleries.

Signac, who led a long and prolific life (1863-1935), suffered grievously from his association with Seurat, his slightly older contemporary, who first put dots on canvas as pointillism, or divisionism. Seurat died young at 30, having completed only a small number of paintings - a familiar combination leading inevitably either to obscurity or to iconic status. For him, it was the latter, and poor Signac was left to become the movement's principal theorist and practitioner. The huge French retrospective at the Grand Palais was vigorously marketed as the revival of a reputation constantly and unfairly overshadowed by the genius of Seurat; the opening section of the catalogue for that show is headed "Loin de Seurat".

In fact, neither tactic really works, but it surely doesn't matter. Seurat's perception of humanity, his understanding of bourgeois life and his sharp interpretation of urban landscapes and forms of escapism made his slender output one of the most tantalising and frustrating oeuvres in 19th-century art. For Signac not to be in Seurat's class is no disgrace, and he should be enjoyed for what he is - divisionist and leader of the French neo-impressionist second division.

Pictures by a major painter from a single source often make for a restricted, or even dull, exhibition, but happily, the obsession of a solitary American collector has proved of value to the museum world. The Courtauld show consists of nearly 50 Signac watercolours and drawings, selected from the 133 works recently presented to the Arkansas Art Center at Little Rock by James T Dyke. "I strongly suspect that Paul Signac and I share common personality types. I do not know that he would share my introversion, but I am struck by a strong sense of detachment in his choice of format, often in the viewing distance of the subject," Dyke wrote.

He has collected wisely and well. There is a fine representation here of Signac's non-pointillist work. Although Signac painted a handful of watercolours with a few random splodges and dashes, on the whole he eschewed pointillism in this medium. The only dots on show are in his marvellous lithograph The Programme of the Theatre Libre of 1888/89, created as a poster advertising Cercle chromatique, a book by his collaborator and fellow theorist Charles Henry. It is not only a strikingly original and advanced piece of graphic design, but a key illustration of pointillist technique. It is also a witty advertisement for a theatre in which we see the head of a man gazing, raptly, at the flaring footlights, which exploit all the shaded colours of the spectrum.

The era's most influential art critic, a war ministry clerk called Felix Feneon, wrote that it elegantly brought together typography, costume, architecture, decor, love and all the industrial arts. "M Paul Signac's poster is a first attempt: his Polychromatism is perfectly organised." Feneon was spot on here, as in other matters, and if Signac had done nothing else, this lithograph would have ensured his immortality.

The absence of dots in the watercolours acts as a form of self-restriction for Signac; almost a self-censorship of the exuberance of his best oil painting, in which he pursued the joys of pure colour almost as an end in itself.

He has a particular feeling for ports, rivers, the sea, ships and sailing boats. Venice, Saint-Tropez, Rotterdam, Marseilles, Antibes, Juan-les-Pins, La Rochelle, even Constantinople, are recorded with an infectious enthusiasm. You need only look at his 1910 view of Antibes to fall in love with both the place and painting, and there is a stunning sketch of Venice and La Salute. Signac was not a particularly modest man; artists who write so authoritatively and even dogmatically about the nature of their kind of painting rarely are. Yet there is something totally captivating about that particular watercolour and its inscription. Just as Sickert occasionally copied Whistler in his etchings of Venice, in this case, Signac's small watercolour, only 16 centimetres by 20, is a copy of a work by Turner on the same subject in the V&A. On it, Signac has written: "cette pauvre petite priere a notre Dieu Turner". You have to like the man as well as admire him.

"Paul Signac: travels in France" is at the Courtauld Institute, Somerset House, London WC2 (020 7848 2526) until 19 August