June 27, 1913] 



SCIENCE 



987 



series, and ends with either white, black or 

 neutral gray, according- to the character of the 

 modification under consideration. The na- 

 ture of these secondary series will be under- 

 stood from the details that follow. 



Neutral gray is defined by the author as 

 " being the gray resulting from mixture (on 

 the color wheel) of the three primary colors 

 (red 32, green 42, violet 26 per cent., which 

 in relative darkness equals black 79.5, white 

 20.5 per cent.)." It may also be described 

 roughly as follows : If by means of a white 

 and a black disk on the color wheel a series of 

 grays be prepared extending from white to 

 black, the visual difference between each of 

 the successive elements of the series being the 

 same, the middle member of this series would 

 be neutral gray. In other words, and roughly 

 speaking, neutral gray is optically half way 

 between white and black.' 



The first of the three modifications of the 

 fundamental series above mentioned consists 

 of mixing the colors of the fundamental series 

 with neutral gray. This produces a contin- 

 uous series of " broken," or dull, colors. 

 Since it is manifestly impossible to illustrate 

 on the color plates every infinitesimal element 

 of such a series, it becomes necessary to choose 

 certain points in such series as standards. 

 This choice is based on considerations similar 

 to those involved in breaking up the original 

 fundamental series into segments. Five dif- 

 ferent admixtures of neutral gray were used, 

 giving five series of broken colors. The ele- 

 ments of the fundamental series are designated 

 in the scheme of nomenclature adopted by the 

 cardinal numerals from 1 to 72, only those 

 designated by the odd numbers being illus- 

 trated on the color plates. The first series of 

 broken colors, which are obtained from the 

 fundamental series by the admixture of 32 

 per cent, of neutral gray, are designated by the 

 primed numbers from 1' to 71'. The second 

 series of broken colors contain 58 per cent, of 

 neutral gray, and are designated as 1" to 71". 

 The third contains 77 per cent, of neutral gray, 



' Some authorities use this term to mean gray 

 of any shade or tint provided it shows no spec- 

 trum color. 



and are designated by the numbers 1'" to 69'". 

 The fourth, 90 per cent., and designated as 

 1"" to 69"". The fifth, 95.5 per cent., desig- 

 nated as 1""' to 67""'. 



The fundamental series and the five series 

 of broken colors are represented on the color 

 plates by 150 color specimens. These are 

 arranged in sequence, beginning with red of 

 the fundamental series, and running through 

 the spectrum six times. They form a hori- 

 zontal line crossing each plate in the middle 

 of the page, and constitute the middle ele- 

 ments of vertical series extending above and 

 below them as follows: 



Extending upward from each of these 150 

 color specimens is a series of " tints " of that 

 particular color. These tints are obtained by 

 mixing each of the 150 colors mentioned with 

 white. Three tints of each color are shown, 

 the first being obtained by mixing with the 

 original colors of the series 9.5 per cent, of 

 white, the second by the admixture of 22.5 

 and the third of 45 per cent, of white. Above 

 the last tint in each vertical series is a speci- 

 men of white. 



Extending dovniward from each of the 150 

 middle elements described above is a series of 

 " shades " of these elements. The first of 

 these shades is obtained in each case by the 

 admixture of 45 per cent, of black with the 

 original color of the middle series. The sec- 

 ond shade contains 70.5 per cent, of black, 

 and the third 87.5 per cent. At the bottom 

 of each vertical column is a specimen of 

 black. Eor each of the 150 elements obtained 

 from the fundamental series and the five 

 series of broken colors obtained directly from 

 it by the admixture of neutral gray we there- 

 fore have a vertical series of shades and tints 

 of that color. Each vertical series extends 

 from white to black, the middle point being 

 one of the 150 middle elements of the scheme 

 of classification. This arrangement of the 

 colors greatly facilitates the comparison of 

 any object with the 1,115 color standards illus- 

 trated in the color plates with a view to deter- 

 mining and recording its color. 



The system of nomenclature used by the 

 author has already been partially detailed 



