At MP I:305 Ruskin refers to the 'fidelity of rock drawing' on which Salvator Rosa's reputation has been built. According to Ruskin in 1853, Salvator Rosa was one of those vanquished by Turner 'each in his own peculiar field, Vandevelde on the sea, Salvator among rocks, and Cuyp on lowland rivers' (Lecture Turner and his Works in Works, 12.127). Instead of truth Rosa, according to Ruskin, offered conventionalism, painting 'such kind of mountain scenery as people could conceive, who lived in towns in the seventeenth century'. (Lecture: Pre-Raphaelitism in Works, 12.369). However, Rosa's letters about his travels suggest that Rosa's response to 'picturesque' landscape was based on more experience than Ruskin credits; perhaps Rosa's knowledge of the Apennines was greater than Ruskin's.
The painting by Rosa, No. 220 of the Dulwich Gallery, is cited as evidence for the mechanical and unscientific treatment of rocks and mountains by Rosa. The thrust of the argument is the same as that directed against Canaletto 's mechanical treatment of water.