Xlvi INTRODUCTION. 



most probable value, taking into account the recently determined relation 

 between the liter and the cubic decimeter,^ is as already stated, A = 13.5951 

 and this value is here adopted. 



8 Is the density of dry air at o°C under the pressure of a column of 

 mercury B,i and under standard gravity. The value adopted by the In- 

 ternational Bureau of Weights and Measures for air under the above con- 

 ditions and free from CO2 is S =0.0012928 grams per cubic centimeter.^ 

 This is in close agreement with the value (8 = 0.00129278) used in pre- 

 vious editions of these tables. For air containing 4 parts in loooo of CO, 

 it gives a density of 0.00129307, and for air containing 3 parts in loooo 

 of CO., the proportion adopted by Hann,^ it gives a density of 0.00129301. 

 Therefore, the value adopted for the density of air containing an average 

 amount of CO2 is 



5 = 0.0012930 



M (Modulus of common logarithms) = 0.4342945. These numbers 

 give for the value of the barometric constant 



K = 18400 meters. 



For the remaining constants, the following values have been used: 

 a = 0.00367 for 1° Centigrade. (International Bureau of Weights and 



Measures: Travaiix et Memoires, t. I, p. A. 54.) 



y = k cos 24> — k' COS" 2(t> + C = 0.002640 cos 2<t> — O.OOOOO7 COS^ 2(t> + 



0.000045 

 R ■= 6367324 meters. (A. R. Clarke: Geodesy, 8°, Oxford, i< 



n = — -^ =0.002396. (Ferrel: Report Chief Signal Officer, 1885, pt. 2, 

 R 



pp. 17 and 393.) 



TABLES 61, 52, 63, 64, 55. 

 THE DETERMINATION OF HEIGHTS BY THE BAROMETER. 



Tables 51 , 52, 53, 54, 55. 



English Measures. 



Since a barometric determination of the height will rarely be made at 

 a place where gi is known, the discussion which follows will be confined to 

 the second form of the barometric formula developed in the preceding sec- 

 tion (see ])age xlv). For convenience in computing heights it is arranged 

 in the following form: 



Z ^ K{\ogB,-\ogB] 



(l + a^) 



(1+^) 



(I + kcoS2(f> - k'cOS^2 4>-\-C){l + r,) 

 Z + 2 //, 



I + 



R 



1 Comptes Rendus, Quatrieme Conference Generale Poids et Mesures, 1907, pp. 60-61. 



2 Leduc, A. La masse du litre d'air dans les conditions nonnales. Comite international 

 des poids et mesures. Travaux et memoires, T. 16, 1917. 



^ Lehrbuch der Meteorologie, dritte Auflage, 1915, s. 5. 



