IN his book ``The Englishness of English Art,'' Nikolaus Pevsner referred to that ``English speciality'' (of the 18th century and earlier) ``the open-air portrait.'' He said that no other country had produced anything like it, not, at least, until the French Impressionists in the 1860s and '70s. He gave examples - such entirely English paintings as Joseph Wright's ``Brooke Boothby'' and Gainsborough's ``Morning Walk.'' He also pointed to the ``same delight in fresh air'' in Scottish painting. This was epitomized for him by Raeburn's ```Sir John and Lady Clerk' walking through their possessions and no doubt discussing improvements.'' This splendid picture, painted in 1792, is one of the most striking works included in the recent exhibition of ``Painting in Scotland: The Golden Age 1707-1843'' at the Tate Gallery, London. As Pevsner pointed out, it is indeed part of the British (rather than strictly English) tradition of outdoor portraiture. Wealthy landowners liked the idea of going down to posterity as lords of all they surveyed: Pride in possessions was certainly the motive, and often the essential grandeur of such works. But there is more than an undercurrent in many of them of an identification with nature, a real feeling for landscape as part of a civilized human being's appreciation of life.
Raeburn's remarkable painting links its human subjects with a sweep of Scottish countryside that, for a painter who never painted landscape for its own sake, displays a memorable awareness of the excitement of the big outdoors. Since the artist is known to have been an enthusiastic follower of such pastimes as golf, archery, angling, and gardening, this is hardly surprising. The landscape in this painting is theatrical and generalized, certainly, even though it has been identified as the Clerks' estate at Penicuik (not far south of Edinburgh).
But more significant is the fact that the Penicuik landscape had inspired a pastoral drama called ``The Gentle Shepherd,'' written by Allan Ramsay (the father of the man with the same name who, before Raeburn, was considered the leading Scottish portrait painter). In other words, it helps in the understanding of this grand picture to know that Raeburn must have been conscious that this panorama had wider associations than those of mere family ownership and of a typical ``English'' delight in ``improving'' or landscaping it. Its links with pastoral poetry of the recent Scottishness of the baronet and his wife - painted with such an attention to their peculiar individualities rather than in some idealized manner - is seen as rooted in the land, as identified with it.
Raeburn's sensitivity to the effects of light also plays an important part in this linking of the foreground couple with the background: They are lit from behind, by the same silvery, winterish light that pervades the brown hills and the sky. It is the subtlety of this light, coolly touching their faces, hands, and clothes, that makes this painting so distinctive; it is also remarkably true to the kind of light experienced in Scotland while the sky is still partly clouded over after a heavy rainfall. The reflected light in the shadowy parts of the Clerks' features, and of Lady Clerk's magically painted white dress, also has remarkable tonal accuracy.
Raeburn has been dubbed ``the Scottish Reynolds'' and he was undoubtedly influenced by the London portraitist. It is even possible that the portrait of Commodore Augustus Keppel Reynolds painted in the 1750s, showing the commodore striding heroically through a landscape of rocky shoreline washed by a tempest-tossed sea, helped form Raeburn's concept of ``Sir John and Lady Clerk'': There are similarities.
But while the Scot also followed in Reynolds's footsteps by visiting Italy, he was much less affected by the experience. And, returning to Scotland, he worked out his own style quite independently of southern influences. There is a realism already appearing in even a fairly early Raeburn like ``the Clerks'' which Reynolds never assumed. And for the origins of the romantic Scottishness of the picture, one also has to look somewhere else.
In his absorbing catalog - really a book in its scope - introducing the ``Painting in Scotland: The Golden Age'' exhibition, Duncan Macmillan argues that Rae-burn's initial mentors in Scotland itself were probably not so much (as traditionally held) David Martin, as the amateur etcher David Deuchar and the painter Alexander Runciman, both working in Edinburgh.
The exhibition and catalog give some space to Runciman, who emerges as a rather amazing artist whose works caught the primitive wildness of the concocted translations of a Gaelic poet called ``Ossian'' published in the early 1760s by James Macpherson. The drawings, which are now the chief remaining evidence of Runciman's style, are full of freedom and mannerism, tall windblown figures with swirling draperies, heroic and expressionistic. In feeling they fall somewhere between the worlds of Michelangelo and William Blake.
Sometimes Runciman's figures move through dramatic landscapes imaginatively in keeping with Mac-pherson's description of the kind of place in which might be found ``an ancient and unmixed race of men'' whose ``language is pure and original.'' We are to ``look for these,'' he wrote, ``among the mountains and inaccessible parts of a country'' - in other words, Scotland - ``places, on account of their barrenness, uninviting to an enemy.'' Macpherson goes on to aver that the inhabitants of Scotland ``differ materially from those who possess the low and more fertile parts of the kingdom.''
Is it too fanciful to suggest that Raeburn was, in his painting of Sir John and Lady Clerk of Penicuik, letting his portraitist's imagination dwell to a degree on the Macpherson/Ossian view of his fellow countrymen? There is no doubt that Duncan Macmillan has a strong point when he observes that the ``liveliness of execution and colour,'' the expressiveness, and the trait of painting directly onto canvas without formal drawing were all characteristics shared by both Runciman and Raeburn and were therefore likely to have been instilled by one in the other. But there is something else that must surely have a bearing on Raeburn's picture.
The place Runciman decorated with his Ossianic paintings (they were unfortunately destroyed by fire in the 19th century) was none other than Penicuik House, family seat of the Clerks. He had decorated ``Ossian's Hall'' at Penicuik for the third baronet, Sir James Clerk. Now Raeburn was portraying Sir John, the fourth baronet. He couldn't possibly have done so without an awareness of the Runciman decorations. The particular exhilaration of Raeburn's portrait certainly owes something to theirs - and to their Scottishness.