ABSTRACTS 



Authors of scientific papers are requested to see that abstracts, preferably 

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 this issue. 



PHOTOMETRY. — An "average eye" for heterochromatic photometry, 

 and a comparison of a flicker and an equality-of -brightness pho- 

 tometer. E. C. Crittenden and F. K. Richtmyer. Bureau of 

 Standards Scientific Paper No. 299 (Bull. Bur. Stds., 14: 87-113). 

 1917. 

 The comparison of lights of different colors is supposed to be based 

 on an "average normal eye." This paper records an attempt to ap- 

 proximate the results of such an eye with typical color differences by 

 using a large number of observers. In particular, results obtained by 

 a flicker photometer and by an equality-of-brightness photometer, 

 with different degress of color difference, are compared. In terms of 

 the Ives-Kingsbury test solutions, for which the proposed normal 

 ratio of transmissions (with a 4 wpc. carbon lamp) is 1.00, the average 

 of 114 observers gives a ratio of 0.99. By using these test solutions 

 results obtained on the flicker photometer by a small number of obser- 

 vers can be corrected so as to give normal values with a high degree of 

 accuracy. On the average, equality-of-brightness measurements also 

 vary in proportion to the test ratio, but erratic variations often over- 

 shadow these systematic differences. For sources having relatively 

 high intensity in the blue, flicker values tend to fall below those ob- 

 tained on the usual standard photometers, but the difference is com- 

 parable in magnitude with the uncertainty of the latter values. 



E. C. C. 



GEOLOGY. — Anticlines in the Blackfeet Indian Reservatioyi, Montana. 



Eugene Stebinger. U. S. Geological Survey Bulletin 641-J. 



Pp. 281-305, with 2 plates and one figure. 1917. 



This paper gives a brief account of the geologic formations in the 



Blackfeet Reservation and of their geologic structure, and a more de- 



264 



