NATURAL PHILOSOPHY. 1G1 



relative to the components of light, which he said consisted of seven colors, 

 red, orange, yellow, green, blue, indigo, and violet. It is now distinctly 

 proved that four of these seven colors of the spectrum are the result of the 

 combination of the three colors now known as the primitive colors, viz., ml, 

 blue, and yellow. Thus, blue and red combined, produce purple or indigo; 

 blue and yellow, green ; while red and yellow produce orange : these facts 

 being known, it is easy to prove that there are not seven, but three primitive, 

 and four secondary, called complementary, colors. 



Several proofs can be given that light is composed of three colors only. 

 One of the most simple consists in placing pieces of blue, red, and yellow 

 papers on a circular disk, and rotating it rapidly, the effect of the eye being 

 to produce a disk of white light. If, therefore, the eye can be deceived so 

 readily while the disk travels at so slow a rate, what must necessarily be the 

 case when it is remembered that light proceeds at the rate of 190,000 miles 

 per second ? 



The rapidity with which light travels is such that the eye is not able to 

 perceive either the blue, red, or yellow, the nerves of the retina not being 

 sensitive enough to receive and convey successively to the mind the three or 

 seven colors of which the light is composed. 



Before entering into the laws of color, Mr. Grace Calvert stated that it 

 might be interesting to know what scientific minds had devoted attention to 

 the laws of colors. 



BufFon followed Xewton, and his researches had special reference to what 

 M. Clievreul had called the " successive contrasts " of colors. 



Father Scherffcr, a monk, also Avrote on the laws of color. Goethe, the 

 poet, also brought his mind to bear upon the subject, and studied it to a 

 great extent. Count Rumford, about the end of the eighteenth century, 

 published several memoirs on the laws of colors. He explained very satis- 

 factorily the " successive " contrast, and arrived at some insight into the 

 " simultaneous " one; still he did not lay down its real laws. 



1'rieur, Leblanc, Harris, and Field, were also writers of most interesting 

 works on this subject. The reason that they did not arrive at the definite 

 laws of color was because they had not divided those laws into successive, 

 simultaneous, and mixed contrasts. These form the basis of the practical 

 laws of color, and the honor of their discovery is due to M. Chevreul. 



The reason why a surface appears white or brilliant, is, that a large portion 

 of the light which falls on its surface is reflected on the retina, and in such 

 a quantity as gives to the surface a brilliant aspect; whilst in plain white 

 surfaces, the rays of light being diffused in all directions, and a small portion 

 only arriving to the eye, the surface does not appear brilliant. The influence 

 of colors on these two kinds of surfaces is very different, as may be perceived 

 by the examples round the room, showing the influence of different colors 

 on gold ornaments. When rays of light, instead of being reflected, are 

 absorbed by a surface or substance, it appears black; therefore white and 

 black are not colors, as they are due to the reflection or absorption of unde- 

 composed light. It is easy to understand why a surface appears blue: it is 

 due to the property which the surface has to reflect only blue rays, whilst it 

 absorbs the yellow and red rays; and if a certain portion of light is reflected 

 with one of the colored rays, it will decrease its intensity; thus, red rays with 

 white ones produce pink. On the contrary, if a quantity of undecomposed 

 light is absorbed, black is produced, which, by tarnishing the color and 

 making it appear darker, generates dark reds, blues, or yellows. The second- 



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