APEIL15, 1898.] 



SCIENCE. 



515 



that additional color h3^potheses will con- 

 tinue to appear until from their abundance 

 they cease to receive attention. 



Competition is the normal condition of 

 progress. ' Lernfreiheit ' is, and must con- 

 tinue to be, the watchword of the student 

 of science. In the evolution of psychology 

 every hypothesis has a right to announce- 

 ment. Whether it drops at once out of 

 sight, or receives general and serious con- 

 sideration, must depend upon its consist- 

 ency as judged by those whose fitness to 

 judge has been demonstrated. . The workers 

 in neighboring departments must content 

 themselves with suspense of judgment until 

 the result of the survival of the fittest is 

 established. 



Assuming, then, that in the present con- 

 dition of disagreement among psycholo- 

 gists the oldest hypothesis of color vision is 

 apt to continue in favor among physicists, 

 it may be well to note a few points upon 

 which we may be justly dissatisfied with 

 it, these points being taken chiefly on phys- 

 ical rather than psychological grounds. 



According to the Young-Helmholtz hy- 

 pothesis in its modern form there are three 

 fundamental color sensations, which may 

 be expressed graphically by overlapping 

 curves of intensity. The simultaneous 

 excitement of all three in appropriate pro- 

 portion gives the sensation of whiteness. 

 The deficiency of the retina in capacity to 

 respond to one or more of the stimuli cor- 

 responding to these sensations determines 

 a special kind and degree of color-blind- 

 ness. 



This idea of fundamental sensations has 

 a rather peculiar history, as was pointed 

 out more than twenty years ago {Am. 

 Journal of Science, April, 1875) by the late 

 Professor A. M. Mayer. Dr. Thomas 

 Young was a contemporary of Dr. Wollas- 

 ton, the discoverer of the dark lines in the 

 solar spectrum. JSTewton had considered 

 the spectrum to be made up of seven colors. 



Of these red, yellow and blue were thought 

 the most important, and were called pri- 

 mary colors, not with reference to any theory 

 of color perception, but because by mix- 

 ture of pigments of these three hues in 

 suitable proportions all the other hues 

 could be obtained, though with loss of pu- 

 rity and especially of brightness. These de- 

 rived colors were, therefore, called second- 

 ary. This ]Srewtonian view is thus not a 

 theory of color vision in any proper sense. 

 Young at first taught the Newtonian view, 

 but subsequently changed his selection of 

 pi'imary colors on account of some erro- 

 neous observations made by Wollaston. In 

 the Bakerian lecture, ' On the Theory of 

 Light and Colors,' read before the Royal 

 Society in 1801, under the heading 'Hypoth- 

 esis III.,' Dr. Young wrote: " The sensa- 

 tion of diiferent colors depends on the dif- 

 ferent frequency of vibrations excited by 

 light in the retina." He further adds : 

 " Now, as it is almost impossible to conceive 

 each sensitive point of the retina to con- 

 tain an infinite number of particles, each 

 capable of vibrating in perfect unison with 

 every possible undulation, it becomes nec- 

 essary to suppose the number limited ; 

 for instance, to the three principal colors, 

 red, yellow and blue, of which the undula- 

 tions are related in magnitude nearly as 

 the numbers 8, 7 aud 6." He thus refers 

 the production of color sensation to the co- 

 vibration, of special particles, set up by 

 waves of special period, just as a tuning 

 fork CO- vibrates with another similar fork 

 sounded in its neighborhood. He supposes 

 that, like the tuning fork, ' each of the par- 

 ticles is capable of being put into motion, 

 less or more forcibly, by undulations dif- 

 fering less or more from perfect unison,' 

 and that ' each sensitive filament of the 

 nerve may consist of these portions, one 

 for each principal color.' 



Dr. Young was avowedly not much given 

 to experiment. He was an acute observer, 



