Trolling through thousands of sketches, drawings, paintings & other artifacts (in digital facsimile) from the hand of J.M.W. Turner, I look the longest at the ones with fewest references to solid objects. Above, the beginnings (or the endings) of landscapes from the late 1820s.
Below, oils from the middle 1830s – grand country house interiors, where the painter was a working guest –
Last, from a sketchbook of 1844-45. The artist, just turning 70, is out on the beach in the rain making watercolors near Folkestone –
The final piece was water-damaged at the Tate in a flood at some point in the 19th century after the artist's death. Splotches not made by Turner are visible around the central section, especially at upper left. But if not for the museum's scrupulousness in noting the source of those marks, nobody would be likely to doubt that they fit with Turner's intention (and with his overall intentional dimness).