The 'unfinished' watercolours in this book were the germinating iridescent centre from which some of Turner's best known works emerged. The Petworth Watercolours, the 'Colour Beginnings', the sketches for 'Rivers of France' and other blue-paper sketches are all famous, yet have never before been reproduced in useful quantity. Here the relevant pencil sketchbooks, carefully but entertainingly annotated, provide a chronological matrix. The range, power, and brilliance of these watercolours will astonish even those who know Turner well through his oil paintings. From his return from Italy in 1820 to the 'Burning of the Houses of Parliament' in 1834, we see his work rise to a level rarely equalled in the story of art. In his colour sketches Turner reaches out to the precarious edges of artistic achievement.