The whole page is taken up with the following notes:
Scondary lights are those either reflecting | from or on a polished body [...] the | effulgence of the sun’s beams or when | his beams are [?concentrated] in the [...] | the Moons beams. The light emited | or reflected by all polished Bodies | according the their textures [...] | density or power of Reflecting –
To attempt to define what | is the reflective power of the suns beam | would be useless as far as relates to their | [?distinction] of Reflective power for we all | know that polished bodies give and receive | light and [?the that] pass light upon a dense | and nugatary power (of Reflecting) yet
This is the first passage in a sequence of notes and diagrams which continues back through the sketchbook to folio 72 verso (D07473). The text continues on folio 78 verso (D07485), following the diagram on folio 79 recto (D07486). The semi-diagrammatic drawing on folio 81 verso (D07491) also appears to belong with these notes, concerned with sunlight or light in general in terms of reflections and the casting of light and shadow from polished objects or bodies of water. They relate to Turner’s fifth Royal Academy perspective lecture, on reflection and refraction.
Davies 1994, p.289.