Drawn with the sketchbook inverted. For a sketch possibly of the same man (?Lieutenant Lewis Roatley, or Roteley, of the Royal Marines), see folio 27 of the sketchbook (D05470; Turner Bequest LXXXIX 20). Turner’s notes describe the tone and set of sails of the various ships for his picture, The Battle of Trafalgar, as Seen from the Mizen Starboard Shrouds of the Victory, exhibited at Turner’s Gallery in 1806 (Tate N00480;1 see the Introduction to this sketchbook). In it the shrouds and sails of the French Redoutable (for which see folio 10, D05457; Turner Bequest LXXXIX 11), alongside the Victory, are indeed dark-coloured and the top sails of the Spanish flagship Santissima Trinidad (see also folio 21 verso, D05458; Turner Bequest LXXXIX 12) are full. The last words refer to flags of the French Fougueux and Bucentaure (see folio 9 verso, D05456) which are not included in the picture.
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Haven and London 1984, p.46 no.58 (pl.68).