176 



SATURDAY LECTURES. 



second of time represent the color we call red, while 789 

 million million vibrations correspond to violet, and so on. 

 An object we call red, therefore, sends to us from the white 

 light falling upon it those waves of the ether which make 

 451 million million vibrations per second. All the other 

 wave lengths of the ether are lost, and most probably by- 

 having their motion converted into a molecular vibration 

 of the substance of the object. 



When we call to mind the great number of separate colors 

 and the infinite variety of their shades, which we recognize 

 as distinct sensations, we at once appreciate the extraordi- 

 nary delicacy of perception by the visual apparatus. 



The satisfactory explanation of color perception has al- 

 ways been among the most difficult problems with which 

 the physiologist has had to deal. The theory on this sub- 

 ject which has held the longest sway over the largest num- 

 ber of minds is that of Young, as revived by Helmholtz. 

 Until within the last few years few or no physiologists had 

 the temerity to doubt the sufficiency of this hypotliesis. 



This theory starts out on the basis that there are three 

 fundamental or primary colors, by the proper admixture of 

 which all other colors and shades of colors can be produced. 

 It is now the popular opinion, wdiich Avas formerl}^ upheld 

 by scientific authority, that these so-called primary colors 

 are red, yellow, and blue, because from a mixture of pig- 

 ments of these colors the painter can produce a large num- 

 ber of the colors he finds of use in the practice of his art. 

 When, however, we come to deal with the pure colors of- the 

 spectrum we find that these are not the fundamental colors. 

 It has been found that from the mixture of spectral red, 

 green, and violet, all the other colors of the spectrum can be 

 produced, and, also, that when these colors are mixed in due 

 proportion white is the result. For this reason, red, green, 

 and violet have been accepted as the primary colors by 

 most modern scientists. 



Newton believed that the particles representing the indi- 

 vidual colors (according to his emission theory) affected the 

 retina " according to their nature and bigness," but Young 



