View this artwork by appointment, at Tate Britain's Prints and Drawings Rooms
Turner referred to this study, inverted relative to the sketchbook’s foliation, for his watercolour of the Inside of the Chapter House of Salisbury Cathedral, exhibited at the Royal Academy in 1799 (Whitworth Art Gallery, Manchester).1
Andrew Wilton, J.M.W. Turner: His Life and Work, Fribourg 1979, p.321 no.199, pl.45.
There is a brown colour trial at the bottom right.