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This makeshift ruler is not mentioned in Finberg’s Turner Bequest Inventory.1 The left-hand, outer edge of the page serves as the beginning of the scale, and there is a further isolated mark near the gutter a little lower down, measuring twelve inches (a foot or 305 mm) from the left-hand edge. These measurements were perhaps used to gauge or check the dimensions of drawings in progress on separate sheets.
See A.J. Finberg, A Complete Inventory of the Drawings of the Turner Bequest, London 1909, vol.I, p.447.
Across the lower half of the sheet there is some scattered watercolour offsetting from the half-completed composition on folio 2 recto opposite (D12263).