PATTERNS CONSPICUOUS IN NATURE. 



389 



to black : find the background against which black and white 

 are equally visible under some natural condition of lighting — 

 for instance, in a wood ; now compare this background with 



Text-fiffui-e 4. 





H — 4— 





V«) 



-O,- 





'N.-Cd- 



>4 



V - 



X' 



Q- - 



- - + 



/ ' 

 / 



_--o/ 



JO^ 



(.r 



Diagram showing the correspondence between the visibility of objects of different 

 shapes (circle, square, isosceles triangle, and rectangles) and the concentration 

 of their areas. 



Experiment No. 5. 



Candles 1 ft. apart ; objects distant from candles 1 ft. 6 ins. 



Objects of black needle-paper, area 16 sq. mm. ; background of white Bristol board. 



Objects. Distance at which Inverse figures, 

 visible, in feet. 



Circle 59 170 



Square 58 173 



Isosceles triangle of 90° ... 53 190 



Rectangle, 8X2 51 198 



Rectangle, 16X1 38 263 



(Mean of five readings to nearest whole number.) 



Proc. Zool. Soc— 1916, No. XXVI. 26 



