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SCIENCE. 



[N. S. Vol. VII. No. ITZ. 



and highly original, but he avows : " For 

 my part, it is my pride and pleasure, as far 

 as I am able, to supersede the necessity of 

 experiments, and more especially of expen- 

 sive ones." Wollaston, in 1802, undertook 

 his observations on the solar spectrum, 

 using a prism of flint glass, a substance at 

 that time comparatively new, hard to ob- 

 tain in large pieces, and often blemished 

 with veins. It is not surprising that his 

 work should have been crude in comparison 

 with that of the skillful optician, Fraun- 

 hofer, who a dozen years later rediscovered 

 the solar lines and mapped them. Of the 

 few lines discovered by Wollaston the most 

 prominent were considered by him to mark 

 the natural boundaries between the chief 

 spectral colors. The A line, if we may 

 here use Fraunhofer's notation, was thought 

 by Wollaston to be the exact limit of the 

 red ; the D line to separate red from green ; 

 the G and H lines to be the natural bound- 

 aries of the violet. In Young's Natural 

 Philosophy, published in 1807, he refers to 

 the work of Wollaston, who, he says, ' has 

 determined the division of the colored 

 image or spectrum in a much more accurate 

 manner than had been done before.' Ee- 

 ferring to Wollaston's method, he adds : 

 " The spectrum formed in this manner con- 

 sists of four colors only, red, green, blue 

 and violet." Referring to some of New- 

 ton's work in obtaining secondary hues he 

 concludes : " We may consider white light 

 as composed of a mixture of red, green and 

 violet, only in the proportion of about two 

 parts red, four green and one violet, with 

 respect to the quantity or intensity of the 

 sensations produced." In this volume Dr. 

 Young makes no reference to the hypothesis 

 of color perception which he had advanced 

 in his Bakerian lecture a few years pre- 

 viously. Whether he had given it up or 

 not is left to inference only. Despite his 

 apparent indifference to experiments, he 

 seems to have set the example, between 



1802 and 1807, of appealing to the rotation 

 of disks to show that gray may be obtained 

 by the mixture of red, green and violet, 

 quite as well as with Newton's seven colors, 

 red, orange, yellow, green, blue, indigo and 

 violet. He says : " The sensations of 

 various kinds of light may also be com- 

 bined in a still more satisfactory manner by 

 painting the surface of a circle with differ- 

 ent colors, in any way that may be desired, 

 and causing it to revolve with such rapidity 

 that the whole may assume the appearance 

 of a single tint, or of a combination of 

 tints, resulting from the mixture of the 

 colors." Half a century seems to have 

 elapsed before this fruitful method was 

 taken up again by Maxwell and Helmholtz, 

 and its valuable results have been still fur- 

 ther extended by Eood, Abney and others. 

 When Helmholtz discovered the long- 

 forgotten theory of Young he was professor 

 of physiology at Heidelberg. The respect 

 in which he is held by all physicists has 

 very naturally caused them to repose confi- 

 dence in the conclusions reached by him as 

 a physiologist. This fact creates quite gen- 

 erally a prejudice in favor of the hypothesis 

 of Young, which is accepted by them as a 

 working hypothesis, even though its as- 

 sumptions be far from proved. It has the 

 merit of great simplicity. It can be grasped 

 without any extended study of the techni- 

 calities of psychology. This is obviously 

 no argument to prove its truth, but in the 

 present condition of the subject, in the con- 

 fusing multiplicity of color hypotheses and 

 the apparent hopelessness of the struggle to 

 establish anything definite that psychol- 

 ogists will agree upon as a substitute 

 for the hypothesis which Helmholtz has 

 offered to the physicists, simplicity with ad- 

 mitted uncertainty is for many of us pref- 

 erable to the championing of a new hy- 

 pothesis which is challenged by half a dozen 

 other hypotheses supported by names of 

 varying authority in the world of science.. 



