according to the author's conception of them.[1] These six disks were then placed against a suitable background (a neutral gray), in spectrum sequence, with wide intervals for the accommodation of connecting series of disks, which were then colored so as to represent an apparently even transition from one to the other. When this very difficult task had been done as well as the eye alone could judge, each intermediate was then measured on the color-wheel and the relative proportions (in percentages) of its two component colors recorded. After this had been done for all the intermedite hues each series (the red-orange, orange-yellow, yellow-green, green-blue, blue-violet, and violet-red) was taken separately and a curve constructed on cross-section paper from the recorded ratios. These curves were found to be in all cases more or less irregular or unsymmetrical, but nevertheless were sufficiently near correct to serve as a basis for a symmetrical curve; and after the points out of
- ↑ 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 ehromatologists 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:
This work Average of 9-12 authorities Extreme of 9-12 authorities Mean of 9-12 authorties. Red 644 6770 6440-7028 6734 (10) Orange 598 ± 2 6074 5892-6300 6096 (9) Yellow 577 ± 1 5786 5640-5850 5745 (10) Green 520 ± 10 5235 5050-5335 5193 (11) Blue 473 ± 3 4738 4520-4861 4680 (11) Violet 410 4176 4050-4330 4190 (10) 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.
