This panoramic drawing continues on folio 20 recto opposite (D09921), and again on folio 21 recto (D09922). The lack of landmarks makes the subject difficult to confirm, but it may relate to the succession of hills looking south towards Plymouth from Gunnislake in the background of Turner’s large painting Crossing the Brook, exhibited in 1815 (Tate N00497).1 There is a sketch of similar terrain, directly related to that part of the painting, in the Vale of Heathfield sketchbook (Tate D10274; Turner Bequest CXXXVII 48). For further discussion of various landscape and tree studies in this sketchbook in that context, see under folio 14 recto (D09910).
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Haven and London 1984, pp.93–4 no.130, pl.123 (colour).