Watercolours are generally regarded as a British preserve. We think of Cox and Cotman, of Sandby, Turner and Prout. But what of Moran, Marin and Hassam, or Demuth and Zorach? That these names should not be familiar is no great surprise. All feature in the National Gallery of Scotland's latest offering - a selection of watercolours from the Museum of Fine Arts Boston. All too are American. Alongside the development of British watercolour painting in the 19th century, a similar tradition was being established in the USA. By the time the earliest work in this show - a somewhat uninspired view of the Jersey Flats by James Hamilton - was painted in 1861, the tradition was well established. The real value of this expedition though is not as a comparison with British equivalents, but as a microcosm of the development of American painting in the late 19th and early 20th centuries, made particularly telling by the fact that many of these works were never intended for formal exhibition.
In the course of a progress from Thomas Moran's sublime 1870s Wyoming landscapes to Edward Hopper's anthropomorphised houses of the 1920s, we encounter a few modest masterpieces. The show is of course centred on two large groupings of Singer Sargent's derivative impressionism and Winslow Homer's all-American ruralism. But, amidst all this faux-modeste grandiosity, lest your eye should miss them, be sure to seek out Childe Hassam's Whistlerian Chicago Nocturne of 1893, Marguerite Zorach's Kandinsky-esque 1919 view of Maine and the vertiginous late Romanticism of John la Farge. They must just be a revelation.
National Gallery of Scotland, The Mound, Edinburgh. To 14 July.
Left: detail of John Singer Sargent's Villa di Marlia: Lucca