Studies of shadows on topsails. A main topsail and topgallantsail full and the fore topsail shivered are shown from the port quarter. The sun is shining from the starboard quarter throwing on to the sails a shadow (wider at the bottom than at the top) from the main topmast and topgallantmast, and putting the fore topsail in complete shadow from the main topsail. A shadow on the starboard leech of the main topsail is marked in brown ink ‘ledt’ (note). The direction of the sun is indicated ‘d son soo’.

The studies illustrate the fact that the shadow of a mast on a sail increases in width according as the angle of the sail increases from the transverse until it reaches an angle of 45 degrees when the shadow is half as wide again as the mast.

Below is a rough sketch of a topsail with the inscription referring to the shadow of the topmast.