Contents: (I) Ancient Theories of Visual Perception: The Physics of Vision; The Physiology of Vision; The Psychology of Visual Perception; (II) Optics Proper: Analysis of Direct Vision: The Visual Cone; The Visual Perception of Physical Space; Binocular Vision; (III) Catoptrics: Analysis of Vision by Reflected Rays: The Law of Equal Angles; Multiple Reflections and Multiple Images; The Principles of Image-Location; Image-Formation and Distortion; Visual Effecs from Composite Mirrors; (IV) Dioptrics: Analysis of Vision by Deflected Rays: Observation and Explanation of the Phenomenon; Practical Application: The Problem of Atmospheric Refraction; Image-Location as a Function of the Shape of the Refracting Surface; Size-Distortion; (V) Analysis of the Rainbow and of Burning Mirrors; (VI) Conclusion. Illus.