SIMULTANEOUS CONTRAST. 289 



(c.) Place a small white square or oblong piece of paper on 

 a dull, dead, black surface. Stare steadily at the white square, 

 and observe that the edges appear whiter than the centre. 



(d.) Place side by side a white and black surface. Cut 

 two oblong (IV x J") pieces of grey, yellow, or other coloured 

 paper of exactly the same size, and lay one piece of the 

 grey on the white background, and the other on the black. 

 Observe how much brighter the latter looks owing to 

 contrast. Reverse the pieces, and notice that the same 

 result occurs. Repeat with other colours. 



(e.) Place on a table a small sheet (4" x 4") of red and one 

 of green paper. Cut out of a sheet of red paper two pieces 

 about one inch square, and place them on the two large 

 squares. Observe that the small red square on the green 

 ground appears far brighter and more saturated than the red 

 square on the red ground. 



(f.) Cut a small hole (5x5 mm.) in a piece of coloured 

 paper e.g., red and look through the hole at a sheet of 

 white paper, the hole appears greenish. 



(<?.) On an ordinary mirror place a slip of transparent 

 coloured glass red or green, or any other colour. Hold in 

 front of the coloured glass a narrow strip of white paper; 

 by adjusting the position of the glass in relation to the 

 light, we see two images reflected from the anterior and 

 posterior surface of the mirror ; one has the same colour as 

 the coloured glass, while the other or posterior one has the 

 complementary colour if a red glass be used, the latter is 

 green if a green glass, it is red. Hold in front of the red 

 glass a piece of white paper with black printed matter on it. 

 The black print is seen green in the posterior image. Gum 

 a few narrow strips of white paper (1 mm. in diameter) on 

 black paper, and on holding it up in front of the red glass, 

 as before, the anterior image appears in the complementary 

 of the glass viz., green. 



6. Simultaneous Contrast. 



(a.) Cut out a small oblong of white, or preferably of grey 

 paper, and put it on a large piece of bright green paper 

 (4 inches square); the grey suffers no change. Cover the 

 whole with a thin semi-transparent sheet of tissue paper. 

 The grey oblong appears pink. 



19 



