And then of the Art of Conserving Light, the Lapis Bononiensis is a notable Instance; and so happily were the Sepulchral Lamps of the Ancients.
- As to Colours, 'tis the greatest part of the Art of Dying to be able to make and fix (that is preserve) them; and the Painters and Limners will own it to be no small part of their Skill to be able well to Mix (that is, in effect, to Generate) Colours.
- For Imitation of Light and Colours, 'tis well known how far Perspective with the Art of Limning and Shadowing have gone therein, which all tend some way to the Advance or Improvement of Direct Vision.
Add to all these, That a due Application of Light to the Object renders it Visible, if it were not so before; as appears from a dark Room illuminated; or else makes it better and more truly discernable by the Sense of Seeing, if before it might have been discern'd.
Hence the same Colour, in a diverse Light, will appear different, and no Picture can well be discern'd or judg'd of but by its true Light. Besides, the Limner will assure you, that he can hardly make true Work, or hit the Air of a Face exactly, unless he draw by a North-Light, by reason of the steadiness of that, and the uncertainty of all other Lights whatsoever.
Which things shew, that the Art of duly applying Light to the Object does very much help and improve Vision. So also does the due placing of the Object, as to Height and Distance. But to enumerate all things that help Direct Vision, would be infinite.
- Ex parte Organi vel Medii, Direct Vision has been improv'd by making use of a Tube, without Glasses, or a Man's clos'd Hand, to look thro'; which admitting into the Eye only the principal Rays, that come directly from the Object, do very much strengthen and clear the Sight,