CAP. XXIII. (Book 23)
Of Perspective.
PRospective (being a Species of Geometry) is a Science treat∣ing of Visible Lines, and may be divided into three parts, Optica, Sciographica and Specularia.
Optica of two kindes, either Physiological or Grammical.
The Physiological part scearcheth the Vniversal Principles, Causes and Elements of the appearences of things which may be considered three several ways, as Vision is Direct, Reflected or Refracted as when things are seen in Water, Glasses &c.
The Grammical is the Art of Delineation, and is more Ne∣cessary to Painting then the other. It considereth Sight either True or False, and is of three sorts, Anoptica, Optica and Catoptica.
Anoptica is the Art of Delineating Objects elevated above the Horizon, Optica designs those extended Foreright, level with Horizon, and Catoptica those beneath the Horizon, which appear as if they came nearer the Eye below.
Another Species is call'd Sciogrophica; It handleth the Causes, Principles, Elements, and Properties of Shaddows; giving the Reason of the Variety of the Apparitions of the Shapes and I∣mages of Things, according as they are elevated either above, direct against, or beneath; far of or near the Eyes and as by the Laws of Grammica are distributed the Out lines of the Superficies as they ought to be, according to their distance and Situation: so this part considereth the Shaddows of Bodys, ac∣cording as their Superficies are Protuberant, or Depress'd.
The last Species is Specularia, and considereth the Reflections and Refractions of Beams, giving Directions for making Glasses,