MISCELLANEOUS TABLES. IxiX 



Table 94. Relative illumination intensities. table 94. 



The table gives illumination intensities in foot-candles for zenithal 

 sun, sky at sunset, sky at end of civil twilight, zenithal full moon, quarter 

 moon, and starlight, and the ratio of these intensities to the illumination 

 from the zenithal full moon. For the sources of the data see Kimball, Her- 

 bert H., " Duration and Intensity of Twilight," Monthly Weather Review, 

 1916, 44: 614-620. 



MISCELLANEOUS TABLES. 



WEIGHT IN GRAMS OF A CUBIC CENTIMETER OF AIR. 



The following tables (95 to 100) give the factors for computing the 

 weight of a cubic centimeter of air at different temperatures, humidities 

 and pressures. 



= 0.00129305 / £-0.378 e N 

 1 + 0.00367 t \ 760 



in which 8 is the weight of a cubic centimeter of air expressed in grams, 

 under the standard value of gravity (g = 980.665) 

 B is the atmospheric pressure in millimeters, under standard grav- 



_ ity; 



e is the pressure of aqueous vapor in millimeters, under standard 



gravity; 

 t is the temperature in Centigrade degrees. 

 For dry atmospheric air (containing 0.0004 °f its weight of carbonic 

 acid) at a pressure of 760 mm. and temperature o° C, the absolute density, 

 or the weight of one cubic centimeter, is 0.00129305 gram. (International 

 Bureau of Weights and Measures. Travaux et Memoir es, t. I, p. A 54.) See 

 also these Tables, p. xli. 



The weight of a cubic centimeter may also be written as follows: 

 = 0.00129305 / B- Q-378 e 



1 +0.0020389 (/ — 32 ) \ 29.921 



where 8 is defined as before, but B and e are expressed in inches and t in 

 Fahrenheit degrees. Thus by the use of tables based on these two formulae, 

 lines of equal atmospheric density may be drawn for the whole world, no 

 matter whether the original observations are in English or metric measures. 



ENGLISH MEASURES. TABLES 95, 96, 97. 



Table 95. Temperature Term. 



This table gives the values and logarithms of the expression 

 a 0.OO129305 



<>,, 29.921 I+00020389 (t-32°) 



for values of / extending from — 45 F. to + 140 F., the intervals between 

 o° F. and no° F. being i°. 



The tabular values are given to five significant figures. 



