988 



SCIENCE 



[N. S. Vol. XXXVII. No. 965 



above. It is the excellent system of identi- 

 fying each color variation by means of sym- 

 bols which serve to show the location of the 

 color in the scheme of classification that is 

 the most distinctive and original feature of 

 the work. As stated above, each of the 36 

 segments of the fundamental series is desig- 

 nated by the odd numbers 1, 3, 5, etc., to 71, 

 the even numbers being reserved for colors 

 intermediate between them. These same 

 numbers modified by the use of primes are 

 used to designate the same colors modified by 

 the admixture of neutral gray. Thus the 

 color designated as 27'" is number 27 of the 

 fundamental series weakened by tha admix- 

 ture of 77 per cent, of neutral gray (third 

 series of broken colors). 



The tints of any color are designated by 

 the number of the color with the addition of 

 one of the letters a, b, e, d, e, f or g. The 

 three tints of each color illustrated on the 

 plates are designated by the letters b, d and 

 f, the other letters being reserved for tints 

 intermediate between those of the specimens 

 in the book. The shades of a color are sim- 

 ilarly designated by the number followed by 

 one of the letters h to n. Thus, 35" i denotes 

 the thirty-fifth segment of the fundamental 

 series diluted as shown in the second series of 

 broken colors, and further reduced by the 

 admixture of 45 per cent, of black. 



The system thus provides a means of desig- 

 nating not only each of the 1,115 specimens 

 of color given in the plates, but all kinds of 

 intermediates between them, the total exceed- 

 ing 4,000 color variations. The magnitude of 

 this task will be appreciated when it is re- 

 membered that in the author's previous book 

 the number of colors named and illustrated 

 was only 186, while in Milton Bradley's excel- 

 lent little treatise on elementary color there 

 are only 126. 



The problem of choosing just what hues, 

 tints, shades and broken colors should be rep- 

 resented in the color plates presents many 

 practical difficulties. The simplest phase of 

 this problem is that of choosing the particular 

 spectrum hues to be designated by the simple 

 names red, orange, yellow, green, blue and 



violet. The authorities are by no means 

 agreed as to just what part of the spectrum 

 is the reddest part of the red, the greenest 

 part of the green, etc. Thus the red of ten 

 difl^erent authors varies from 644 to 703 X 

 10"' cm. in wave-length. Most of the other 

 colors vary as much according to different 

 authorities. Each author is a law unto him- 

 self in such matters. This is one of the 

 reasons why any system of color standards 

 which will serve the main purpose of such 

 standards, namely, that of identifying the 

 actual colors met with in nature and in the 

 arts, would be eagerly adopted by naturalists, 

 as well as by those who find need of color 

 standards in the arts. 



A much more important difiiculty arises 

 from the fact that certain hues of the funda- 

 mental series require more elements than 

 others in the series of tones between white 

 and black in order to make the optical in- 

 tervals between the tones chosen as standards 

 equal in the different series of tones. The 

 author has chosen to represent three tints and 

 three shades of each of the pure colors. This 

 gives a series of seven elements in each series 

 of tones. Except in the yellows this seems to 

 be very satisfactory, but the eye can distin- 

 guish such small differences of tone in this 

 part of the spectrum that a larger number of 

 elements in the series of tones would have 

 been helpful. In the yellows and greens there 

 is also a considerable optical interval between 

 the darkest shade (containing 95.5 per cent, 

 of black) and the adjacent samples of black. 



The fact that in the series of broken colors 

 the optical intervals between the adjacent 

 hues are less evident than in the full colors 

 also gives rise to a number of practical diffi- 

 culties in determining just what elements to 

 drop out in order to make the intervals of 

 suitable magnitude and still cover the range 

 of color variation in a satisfactory manner. 

 None are omitted in the first and second series 

 of broken colors, but in the third and fourth 

 each alternate hue is omitted, while the fifth 

 series contains only the six hues ordinarily 

 designated as the primary spectrum colors, 

 except that yellow-orange replaces orange as 



