Last Friday visited the Whitworth Art Gallery in Manchester, where they have seven sketchbooks by the eighteenth century English watercolour painter, John Robert Cozens. It so happened that the sketchbooks were being displayed in a glass case in an exhibition entitled The Land Between Us – place, power and dislocation but what was on display was well worth the trip – in particular an especially mouth-watering pencil and wash sketch of Vesuvius as glimpsed from the myrtle plantation at Sir William Hamilton’s villa at Portici, and dated August 18^th, 1782.

In common with other great British watercolourists such as Francis Towne, Thomas Girtin, John Frederick Lewis, John Sell Cotman and Edward Lear – but with the notable exception of Turner - John Robert Cozens is a chronically under appreciated artist. Turner had the grace to say that had Tom Girtin lived he should have starved, and Constable paid a similarly handsome compliment to John Robert Cozens, calling him the greatest genius that ever touched landscape.

John Robert was fortunate to be the son of another artist of originality and distinction, Alexander Cozens, but less fortunate perhaps in his personal demeanour - “of a silent, hesitating disposition, and grave manners” as a contemporary described him. He visited Italy twice, firstly, in 1778, under the patronage of Richard Payne Knight, and secondly in the entourage of the “sensitive, spoiled and unconventional” writer, William Beckford, whose keen sensibility to the scenery and the artistic treasures of Italy were perhaps as much of a trial as an inspiration to the young Cozens. At all events Cozens’s friend the Welsh artist Thomas Jones (another highly original talent, though not in water colour) spoke of Beckford’s departure from Naples in September 1782 as having left Cousins (as he spells the name) “once more a free Agent and loosed from the Shackles of fantastic folly and Caprice.” Beckford later referred to Cozens as an ungrateful scoundrel, for what reason we do not know.

What distinguishes the Portici sketch is the entirely convincing way in which a huge panorama of mountain scenery and flat middle distance has been captured on two leaves of a sketchbook measuring about 18 inches by 9 – with the centrefold running down the middle. It consists of light pencil markings (including words like “woods” and “green & rock”) on laid paper, and then quickly washed over with a grayish wash. Part of its attraction is the speed with which it was evidently executed. There are no signs of erasures or corrections; this is the seemingly effortless work of a superb observer and executant at the top of his form.

If there was one word to describe this sketch it would be the epithet so beloved of the hippy generation, “cool”, a value which was well understood in the eighteenth century, though they preferred to speak in terms of irony, understatement and in general the classical pose of “nil admirari”. You come across it all over the place, in Swift, in Pope, in Fielding, in Gibbon, and in the cut and thrust of daily conversation: “Pray, Mr Quin, do you ever make love?” the Duchess of Queensberry asked the actor James Quin. “No, Madam, I always buy it ready made.”

Up until reading his observations about Cozens in his book Landscape and Memory I’d always been a bit of a fan of Simon Schama’s, but now I’m beginning to have reservations… Quite simply Schama’s version of John Robert is (in my view anyway) almost ludicrously overcooked and over elaborate. The artist comes across as transcendentally self-absorbed and angst-ridden, and his works seen as eerie, surreal, hallucinated, unearthly. Disorientation and the scrambling of perception is the key to it: “We have been pulled into a universe of representation where something has got in the way between art and its ostensible object.” To which the skeptical reader (as well as wondering what that something might be) is tempted to respond, “scrambling of perception, indeed.”

This kind of overheated language may be appropriate for the likes of that “bona fide ecstatic” as Schama terms Beckford, but it is not appropriate for J.R. Cozens – even when he is painting his stunning representations of the Alps, or his equally stunning caverns in the Campagna. Schama chooses to dwell on “creative disordering”, but the term “creative ordering” would appear to be just as appropriate. Schama himself is perhaps open to the charge of creative disordering by implying that the artist’s eventual succumbing to mental illness was a natural sequel of an alleged “sensory brinkmanship” brought on by staring into sublimity without wearing sunglasses.

“When John Robert actually faced the mountain summit from the ledges, the imperial prospect that ought to have been yielded up to any confident eighteenth-century enlightened mind rushed past him. His head swam. His brush floated vaporously over the page. His art soared. And when his masterpieces had been accomplished, he went mad.”

Here is vaporous brushwork with a vengeance. Or the kind of swaggering, overconfident verbal pyrotechnics that offer an entertaining caricature of Cozens as yet another unstable, tormented Romantic loony, rather than giving us the real artist who, as Constable said, "touched" landscape. Touched, not twisted be it noted.

By way of postscript it’s worth noting that when Cozens painted the Portici sketch he had just recovered from a bout of malaria. Only a week or two later that amiable and musical lady, Catherine, Sir William Hamilton’s first wife, died. Nine months later her body was brought back to Wales for burial on the family estate at Slebech.