F. L. Tttfts — Photometric Measurements. 533 



A comparison of the figures in the last row of Table II with 

 those in the third row shows at once that the color curve for 

 J. T. has the highest ordinate in the violet-blue. Designating 

 this by 100, the ordinates in the red and green were computed 

 and are given in the third row of Table III. 



Measurements of the relative intensities of the white and 

 colored lights were also made by J. T., using an ordinary 

 wedge photometer in place of the flicker photometer. It was 

 found that he could compare lights of different colors with the 

 ordinary photometer with the same ease that the normal eye 

 could make the comparison by the flicker photometer. The 

 last row in Table I contains the results obtained by J. T. with 

 the ordinary wedge photometer. The fourth row of Table II 

 gives the percentages of the transmitted light calculated from 

 these readings. Considering the small amount of practice the 

 subject had had in photometric measurements, the agreement 

 between these results and those he obtained with the flicker 

 photometer is certainly very good. 



Some measurements were also made on the extent of the 

 visible spectrum and the position of maximum luminosity. 

 The spectrum of an incandescent lamp seemed to J. T. to ex- 

 tend from 6350. Angstrom units, in the red, to 4000 in the 

 violet, while to the writer the same spectrum seemed to extend 

 from 7700 to 3800. For J. T. the position of maximum lumi- 

 nosity seemed to be at wave length 5250, while for the writer 

 it was at 5800. 



Phoenix Physical Laboratory, Columbia University, Oct., 1906. 



