7. Apparent Form of the Dome of the Sky, Ann. d. Physik, 1918, 55, p. 387; Sci. Abs. 1918, No. 1147.
8. Course on Optics, 1738, Robert Smith.
9. Color and Its Applications, 1915 and 1921; Light and Shade and Their Applications, 1916, M. Luckiesh.
10. Report of The Submarine Defense Association, L. T. Bates and L. A. Jones.
11. Marine Camouflage Design, E. L. Warner, Trans. I. E. S. 1919, 14, p. 215.
12. The Visibility of Airplanes, M. Luckiesh, Jour. Frank. Inst. March and April, 1919; also Aerial Photometry, Astrophys. Jour. 1919, 49, p. 108.
13. Jour. Amer. Opt. Soc., E. Karrer, 1921.
The foregoing are only a few references indicated in the text. Hundreds of references are available and obviously it is impracticable to include such a list. The most fruitful sources of references are the general works on psychology. E. B. Titchener’s Experimental Psychology (vol. 1) contains an excellent list. A chapter on Space in William James’ Principles of Psychology (vol. II) will be found of interest to those who wish to delve deeper into visual perception. Other general references are Elements of Physiological Psychology by Ladd and Woodworth; the works of Helmholtz; a contribution by Hering in Hermann’s Handb. d. Phys. Bk. III, part 1; Physiological Psychology by Wundt; E. B. Delabarre, Amer. Jour. Psych. 1898, 9, p. 573; W. Wundt, Täuschungen, p. 157 and Philos. Stud. 1898, 14, p. 1; T. Lipps, Raumaesthetik and Zeit. f. Psych. 1896, 12, 39.