The subject is Norham Castle on the River Tweed, on the borders of England and Scotland. Turner first drew and made of this scene in 1797 and exhibited a finished watercolour of it at the Royal Academy in 1798. A number of other versions of it date from 1802, 1820 and 1825 and Turner made new sketches on the spot in 1831. This remarkable marks the culmination of what seems to have been a lifelong fascination with this place and is one of Turner's greatest of light and atmosphere. In it the solid forms of the and the castle are treated purely as translucent elements of light and colour. The castle itself is rendered in a thin glaze of blue, so fluid that it has run and dripped down the canvas. But although Turner has created some of his most atmospheric effects here, the place is nevertheless immediately recognisable. Furthermore, the compositional structure is strongly , the banks of the river providing balancing foreground forms on each side, with carefully orchestrated recessions into a blue haze beyond the castle and into the pale yellow sunlight in the sky above.
'Norham Castle' is exceptionally well preserved for a Turner oil painting and unlike many of his canvases probably looks very much as it did when it left his easel. Turner would never have exhibited in public a work like this, since it would have been considered too lacking in detail and 'finish' to be acceptable at the Royal Academy. It is possibly a sketch for a more finished picture that Turner may have had in mind, or it could be what is known as a 'lay-in' - the beginnings of a picture which Turner would have worked on much more to make a finished exhibition picture. However, it appears to most people now as a complete and satisfying work in its own right, and it is not impossible that Turner saw it that way and that it is a painting done for his private satisfaction.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.58