abstracts: geology 427 



ruinations of the specific heat and latent heat of several substances 

 in general use as refrigerating media. Heat developed electrically in 

 a coil located in the central axis of the cylindrical shell comprising the 

 calorimeter is distributed by conduction to the calorimeter and contents 

 whose initial and final temperature, when in thermal equilibrium, are 

 measured by a platinum resistance thermometer. Heat from other 

 sources is excluded by enveloping the calorimeter with a metal jacket 

 separated from it by an air space and keeping this jacket during measure- 

 ments at the same temperature as the calorimeter surface, using multiple 

 thermocouples to indicate this equality. The calorimeter is adapted for 

 use between — 50° and +50°C. and for pressures up to 70 atmospheres. 

 The method of manipulation in making measurements of heat capacity 

 is described, and the results of an extended series of observations to 

 determine the heat capacity of the empty calorimeter are given. 



N. S. 0. 



PHYSIOLOGICAL OPTICS.— The relative sensibility of the average 

 eye to light of different colors, and some practical applications to 

 radiation problems. W. W. Coblentz and W. B. Emerson. Bureau 

 of Standards Scientific Paper No. 303 (Bull. Bur. Stds., 14: 167-250) 

 1917. 

 In the present investigation the methods are practically the same as 

 used by previous experimenters. In the visual measurements, the 

 spectral light was compared with a standard white light both by means 

 of a flicker photometer and by means of an equality of brightness pho- 

 tometer. The source of white light was a standarized vacuum tungsten 

 lamp. A cylindrical acetylene flame was used as a source of spectral 

 light. The distribution of energy in the spectrum of the acetylene 

 flame was determined with great care. Visibility curves were obtained 

 on 130 persons, of which number 7 were known to be color blind. 

 The visibility curve of the average eye is wider than previously 

 observed. A mathematical equation of the average visibility is given 

 and applications of these data to physical photometry are made. It is 

 shown that the eye responds to light having an intensity less than 

 1 X lO" 16 watt. W. W. C. 



GEOLOGY. — Structure of the Vicksburg- Jackson area, Mississsippi. 

 Oliver B. Hopkins. U. S. Geological Survey Bulletin 641-D. 

 Pp. 93-120, with 1 plate. 1916. 

 The object of this report is to show which of the- areas in west- 

 central Mississippi that were examined by the Survey are considered 



