II.

LINEAR PERSPECTIVE

General remarks on perspective (40--41).--The elements of perspective:--of the point (42--46).--Of the line (47--48).--The nature of the outline (49).--Definition of perspective (50).--The perception of the object depends on the direction of the eye (51).--Experimental proof of the existence of the pyramid of sight (52--55).--The relations of the distance point to the vanishing point (55--56).--How to measure the pyramid of vision (57).--The production of the pyramid of vision (58--64).--Proof by experiment (65--66).--General conclusions (67).--That the contrary is impossible (68).--A parallel case (69).--The function of the eye, as explained by the camera obscura (70--71).--The practice of perspective (72--73).--Refraction of the rays falling upon the eye (74--75).--The inversion of the images (76).--The intersection of the rays (77--82).--Demonstration of perspective by means of a vertical glass plane (83--85.)--The angle of sight varies with the distance (86--88).--Opposite pyramids in juxtaposition (89).--On simple and complex perspective (90).--The proper distance of objects from the eye (91--92).--The relative size of objects with regard to their distance from the eye (93--98).--The apparent size of objects denned by calculation (99--106).--On natural perspective (107--109).