The whole page is taken up with the following notes:
Primary Light that which is received direct | Second Primary Light into 3 direct Reflected and refracted | Lomazzo gives this to emanation of the Deity radiation [Shanes: or adoration] of Glory | Third Primary Light to artificial light the fire in the | Broiling of St Laurence by Titian when the angle [i.e. angel] have | The Second Light
is that part of a body that evades the direct rays and | and is the stronger as the part which reflects the direct ray | is the broader and more so when it fall upon the <front> [‘back’ inserted above] | of such bodies that are lighted before by the direct ray
In the ray departing again to other bodies or through transparent | bodies as Glass and the more dense the broader but the less [?Dense]
The first paragraph comes from several brief chapters within ‘The Fourth Booke: Of Light’: chapter IIII, ‘Of the Division of Light’, page 142; the second from chapter VI, ‘Of the Second Primarie Light’, pages 144–5; and the last from chapter VII, ‘Of the Third Primary Light’, page 145.
The passage on reflected light is from the single-paragraph chapter X, ‘Of Reflected Light’, on page 149, and that on refracted light (as far as ‘Glass’) from chapter XI, ‘Of Refracted or Broken Light’, pages 149–50. The remainder appears to be taken from the beginning of chapter XII, ‘After What Sort All Bodies Receive Light More or Less’, on page 150: ‘because the elementes are naturally apt to bee charged and mixed with each other, wherefore ... it is most evident, that wheresoever they are found most pure, there the light which falleth upon them, is lesse apparent and more purified; and contrariwise brighter and of greater force, where they are thicker and grosser’.
Ziff 1984, p.49 note 6; see also Davies 1994, p.288; Lomazzo also checked directly.
Shanes 1990, pp.278–9, 371 note 57 (with transcriptions of Turner’s first paragraph and the equivalent passages from Lomazzo); Ruskin gives Turner’s declaration, ‘The Sun is God’: Fors Clavigera, letter 45, September 1874, in E.T. Cook and Alexander Wedderburn (eds.), Library Edition: The Works of John Ruskin: Volume XXVIII: Fors Clavigera: Letters to the Workmen and Labourers of Great Britain: Volume II: Containing Letters 37–72: 1874, 1875, 1876, London 1907, p.147.