346 E.. L. Nichols—A. Study of Pigments. 
under which each pigment is compared, all measurements cam 
be referred to a common unit, i. e. to the intensity of a certain 
region of this spectrum; or, as is generally more convenient, 
each region in the spectra of the pigments can be referred to. 
the “raat ag of the corresponding wave-length in this standard 
8 
ere es test the efficacy of this method four spetepemens pig- 
ments were selected. These were red-lead, 
) 
formed crystals under the microscope. The yellow and green 
were freshly prepared by precipitatiow and the separate parti- 
TABLE. 
ey 2 referred to that o 
e rresponding road Intensity referred to that of the re- 
Region. Tenth oof the spectrum of gion of re 4 line in the spectrum 
light. of white 
bey j : 7 = s + 
Color. (Rood.*) | = = 23 os 2 = ze a” Fs + 
ELSE eee Lee oe 
ie Sian - et a = ~ a = ee ee 
Sy a aanee Nas 6800| 0-815] 0°744) 0°042| .... | 17158] 1-056] 0-060) ..-. | 1421 
Orange-red, .___- 6550! 0-747) 0°718) 0-046! 0-005! 0 996] 0-957) 0-062) 0°007 1333 
range, 50| 0°452) 0°587) 0-061! 07004! 0°515] 0°670 0 068) 0°005 1114 
680) 0-0T7 1 3| 0-006] 0.073] 0°352) 0-211] 0°005) 0°94 
Yellow-green, ..-|5370] .... | 0°170! 0°297/ 0-009] .___-| 0-132) 0°232) 0-006) 0°781 
Green 200 . | 0°026) 0°322| 0-034] .__. | 0-017) 0:225| 0°021| 0°649 
Green-blue 4910] .... | 0°001) 0°184) 0°110 0-001) 0°092 0-055) 0 500 
a PANG. bse yack 4700} 2.) 2. :.:|- 0064) O18] _ | 2. | 0°026) 0-072) 0°400 
LS Sean nya la 2680) co2 [eons CUES OTIS 2] 2 1 6181 80 303 
Violet Se ce whe ed Co 4 || Gees Baieenee ees A oa he faces 47) 0°225 
4330 SOE desea ges Sacer AUIsC) Gt Gale Mais Woamaien Bonn Me Zt 
* Rood, Modern Chromatics, p. 26. + Lamansky (article already cited). 
cles could not be distinguished with a $ inch stig These 
dry pigments were spread to a depth of about 10™™ upon a 
black surface. They were not subjected to any honsiderny® 
in t 
ca 
same manner served as the standard white. The spectrum of 
the light reflected from the rather uneven surfaces thus ob- 
tained was compared with the spectrum of daylight. The 
easurements, the results of which are exhibited in the above 
table and by. the accompanying curves (figure 2) ayes 
potions of the spectrum in which measurements were made are 
esignated by their characteristic colors. The wave-lengths are 
