[1] A " Nomenclature of Colors " for Naturalists, " and " Compendium of Useful Knowledge " for Ornithologists. " By " Robert Ridgway, " Curator, Department of Birds, United States National Museum. " With ten colored plates and seven plates " of outline illustrations. " Boston: " Little, Brown, and Company. " 1886. " (12mo., pp. 129, pls. 17.)

The subject of color and color nomenclature discussed on pages 15-58. Plates i-x, inclusive, represent 186 named colors, hand-painted (stencilled).

[2] Titles of several books on the subject which are especially recommended to the lay student of chromatology are given at the end of this text.

[3] See Science, June 9, 1893, and Nature, Vol. LII, No. 1347, Aug. 22, 1895, pp. 390-392.

[4] According to Aubert more than 1000 hues are distinguishable in the spectrum, though among them all the hues between violet and red are wanting.

[5] That is to say, the practical limit for pictorial representation of the colors in their various modifications.

[6] Milton Bradley: Elementary Color, p. 18.

[7] See colored figure on frontispiece.

[8] See the colored figure on the frontispiece of this work, which clearly illustrates this method of color measurement. Larger disks of spectrum red, green, and violet are interlocked and adjusted so that they present, respectively, 32, 42, and 26 per cent. of the circumference; superimposed on these is a single smaller disk of neutral gray, and on this two still smaller disks of black and white, the former occupying 79, the latter 21, per cent. of the area. The result of this combination of colors, when the disks are rapidly revolved, is that the entire surface becomes a uniform neutral gray precisely like the middle disk, which blends so completely with the color inside and outside its limits that no trace of division can be detected. Hence, neutral gray equals a combination of red 32, green 42, and violet 26 per cent., and also equals a combination of black 79 and white 21 per cent. As further illustrating the point, it may be mentioned that not only does the above-mentioned combination of the three primary colors equal neutral gray but so also does the combination of any color ("secondary" or "tertiary" as well as primary) with its complementary, though the darkness or lightness of the gray varies somewhat, as the following table shows:

[9] The number is doubled so that every other one represents an intermediate hue not shown in color.

[10] Owing to the circumstance that spectrum orange does not, at least when mixed with gray, fairly represent a medium hue between red and orange, being much nearer the former, a hue much near to yellow (yellow-orange, No. 15) has been selected.

[11] For satisfactory color-wheel work it is necessary to discard practically all the so-called artists' colors, as being much too dull to even approximately represent the colors of the spectrum, and to substitute carefully selected aniline or coal-tar dyes, of which, fortunately, there is a very large number of remarkable purity of hue. Indeed, the work of most color-physicists is vitiated by their use of such crude colors as vermilion, carmine, scarlet-lake, chrome yellow, emerald green, Prussian blue, etc. (For a list of dyes and pigments used in preparing the Maxwell disks representing the thirty-six colors of the chromatic scale, see pages 26, 27.)

[12] In fixing the exact position or wave-length of the spectrum colors considerable latitude is allowable, the element of "personal equation"—that is, difference in the conception of different persons as to just where the reddest red, greenest green, etc., are located, accounting for the considerable disagreement among chromatologists as to the wave-lengths. The following table, showing the average, mean, and extreme wave-length of each of the spectrum colors as given by nine or more authorities together with those of the present work (as determined by Dr. P. G. Nutting, Associate Physicist of the U. S. Bureau of Standards) is of interest in this connection:

From this table it will be seen that the red of this work is appreciably more orange than that of others, the orange slightly more yellowish, and the violet a little less bluish than the average; but the author is assured by Dr. Nutting that these standards are exceptionally accurate.

[13] The percentages are given in tables on pages 23 and 25.

[14] That is to say, theoretically. Unfortunately it seems to be beyond the colorists' skill to reproduce true shades of the pure colors, all showing a more or less decided admixture of gray, resulting in a series of broken or dull shades. (See pages 23 and 24.)

[15] Although only 1115 different colors are actually shown on the plates the system is really equivalent to the presentation of considerably more than 4000 distinguishable and designatable colors.

[16] The Theory of Color (American edition, 1876), p. 99.

[17] In the present work the possibility of variation between different copies is wholly eliminated by a very different process of reproduction. Each color, for the entire edition, is painted uniformly on large sheets of paper from a single mixture of pigments, these sheets being then cut into the small squares which represent the colors on the plates.

[18] See Rood: Modern Chromatics, pages 50-52.

[19] Some criticisms of Popular Color Definitions and Suggestions for a better Color Nomenclature. Milton Bradley Co., Springfield, Mass. (Small pamphlet of 15 pages).

[20] Milton Bradley: Elementary Color, p. 25.

[21] Exception has been taken in a recent work ("A Color Notation," by A. H. Munsell) to the use of the term tone in this connection, on the ground that its proper use belongs to music, and the term value is substituted. The same line of reasoning would, however, certainly require the discarding of chromatic scale as a term of music nomenclature, since its derivation is clearly from color (chroma). Furthermore, the word "value" is even more elastic in its application than tone, and, all things considered, the present writer, at least, fails to see that any improvement is made by the proposed change.

[22] The term chromatic scale has unfortunately been appropriated for a very different use (in music); nevertheless it is strictly correct in the present sense while in the other it is not, though firmly established by long usage. The term spectrum scale is not adequate, as a substitute, because the spectrum series of colors is incomplete through absence of the hues connecting violet with red, which are necessary to show the full scale of pure colors and hues.

[23] The distinctions of color or hue diminishing in proportion to the increased admixture of gray, each alternate color or hue, with its scale (vertical) of tones, is omitted from the third and fourth series; while in the fifth the color differentiation is so greatly reduced that only the six spectrum colors (dulled by admixture of 95.5 per cent. of neutral gray), together with purple (the intermediate between violet and red) are given; a yellow orange hue being substituted for spectrum orange because it is more exactly intermediate in hue between red and yellow.

[24] J. J. MÜller found that a mixture of the orange and violet rays of the spectrum produced a whitish red (Rood, "Modern Chromatics," p. 129). The author of the present work, without being at the time aware of this, produced an absolutely pure red (but of reduced intensity) by mixture of either orange and violet (orange 63.5, violet 36.5 per cent. = red 85 + white 15 per cent.), or from orange and the violet-red which is complementary to green (violet-red 51, orange 49 per cent.), the latter equaling red 89 + white 11 per cent; the mixtures being made on a color-wheel with Maxwell disks representing the pure colors of the present work. The red resulting from either of these mixtures on the color-wheel is far purer than the blue resulting from mixture of green and violet, and incomparably more so than the yellow resulting from mixture of either red and green or orange and green. Consequently, if the same results would come from mixing orange and violet light, it is difficult to understand how red can be a primary color according to the accepted definition.

[25] Rood: Modern Chromatics, p. 34.

With the single exception of Vanderpoel (Color Problems, p. 28, plates 3, 4, where yellow is given first in order of luminosity) all authorities on color-physics that I have been able to consult very singularly ignore yellow entirely in their treatment of the subject of luminosity.

[26] All quotations here are from Milton Bradley's "Elementary Color," except where otherwise noted.

[27] As determined by Dr. P. G. Nutting, Associate Physicist, U. S. Bureau of Standards.

[28] See Rood, Modern Chromatics, pages 34, 35.

[29] The aniline or coal-tar dyes named are all of the manufacture of Dr. G. GrÜbler and Co., Leipzig, Germany, unless otherwise stated. (See Preface, page ii.)