The whole page is taken up with the following notes:
Painting is an art which, with proportionable lines and | color answer to the Life by observing the Perspective | Lights doth so imitate the nature of s[...] | that it represents the flatness and the Roundness of all | upon a flat surface | Definition, is that any natural thing consist | of matter and form, answering to Genus and Difference | which logicians declare Genus the essence, and diff | the form and qualities Genus then in painting is | Art. The first reason that the definition of Art itself is | a sure rule of certain things to be made. secondly from | natural things themselves which are rules and indowd | with what their nature is capable of attaining may well | be a certain rule to artificial things
Ne sutor ultra crepidam
The passage to ‘surface’ comes from the introductory paragraph on page 13 to chapter I, ‘The Definition of Painting’ in ‘The First Booke of the Naturall and Artificiall Proportion of Things’. Turner closely follows Lomazzo, although rather than ‘flatness’ the original gives ‘thicknesse’, which makes better sense in the context. Turner’s illegible word beginning with ‘s’ replaces Lomazzo’s ‘corporall thinges’. Notes from this page continue as far as ‘rules’, the rest being taken from page 14. Turner has slightly scrambled Lomazzo’s passage reading ‘a sure and certain rule of thinges to be made’.
The Latin phrase at the end comes from page 16, where Lomazzo retells Pliny’s story of the ancient Greek painter Apelles, criticised by a shoemaker not just over the depiction of a shoe but of other items. Lomazzo’s translater, Richard Haydocke, gives the moral in his marginal note as ‘Let not the Sowter presume beyond his slipper’, a typical modern rendering being ‘Let the cobbler stick to his last’. Ziff notes how Turner ‘pounced’ upon this story of ‘envy and ignorance’ in relation to art, and points out another anecdote in the same vein recorded later in the sketchbook (folio 38 verso; D07418).2