AN IMPROVED COLORIMETER 263 



colors, red, yellow and blue, lowest in intensity, is the one directly 

 matched to the chemical solution taken as a base. The entire 

 series of unit glasses consists of 163 in the red, 146 in the yellow 

 and 155 in the blue. In each of the colors, the series begins at 

 the lightest tint with 0.01, and reaches the deepest shade at 20. 

 The intervals of tint are at first 0.01, then 0.02, finally from 1 

 up to 20, the intervals are 0.05. 



While it is true that absolute purity of color is nowhere 

 obtainable except through the isolation of a solar ray of a wave- 

 length which is interpreted by the eye in terms of that color, 

 yet for practical purposes there are many difficulties in the way 

 of the utilization of the color spectrum as a standard. 



The original tintometer is a very simple instrument consist- 

 ing of a wooden binocular frame without a lens, through which 

 the left eye sees the object the color of which is to be determined, 

 while in a holder at the end of the right hand tube of the binocu- 

 lar are placed colored glass strips, graded in graduated intensi- 

 ties of the three primary colors as stated. From a series of 

 these, those are gradually selected by successive trials, which 

 transmit such a mixture of rays as matches the color of the object 

 seen through the left hand tube. Underneath the color glasses 

 is placed a tray containing chemically pure calcium sulfate, 

 forming a standard white reflecting surface. 



The writer has found the apparatus practically useful for 

 color determinations in the study of color inheritance. In order 

 to render the use of it more practical and convenient, it was 

 found desirable to introduce a number of improvements which 

 have been added to the original apparatus. As the instrument 

 now stands, the writer believes that it will prove practically 

 useful to plant physiologists and geneticists engaged in research 

 work involving color determinations, for the quantitative deter- 

 mination of color. No patents have been applied for on the 

 mechanism and any laboratory is free to make such use of the 

 illustrations and drawings as it may desire. 



The writer's improvements on the original apparatus consist 

 essentially of a mechanism carrying two revolving steel spindles, 

 each holding a glass cylinder capped at its outer end. In these 



