In like manner _Hearing_ may be divided into _Direct_, _Refracted_ and _Reflex'd_; whereto answer three parts of our Doctrine of _Acousticks_, which are yet nameless, unless we call them _Acousticks_, _Diacousticks_, and _Catacousticks_, or (in another Sense, but to as good Purpose) _Phonicks_, _Diaphonicks_, and _Cataphonicks_. I. Direct Vision has been improv'd two ways, _ex parte_ Objecti, and _ex parte_ Organi _vel_ Medii. 1. _Ex parte Objecti_, Direct Vision has receiv'd advantages by the Arts of _Producing_, _Conserving_ and _Imitating Light_ and _Colours_, which are the Objects of Vision. 1. For the Art of _Producing Light_, we have the Frication of all hard Bodies that beget Fire; especially of the Flint and Steel; and instead of the Flint, most hard Stones (as well as the Cane) may be us'd to the same effect, as upon trial I have found. Add hereto the lately invented _Phosphorus_, which is a new and admirable way of producing a _Lucid Substance_ by Art, out of a Body in itself not _Lucid_; and therefore may not unfitly be term'd an _Artificial production_ of _Light_. 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. 2. 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_. 3. 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.