XXll ■ INTRODUCTION. 



In order that pressures thus derived shall be expressed in C.G.S. units it 

 is evident that the recognized standard values of the constants of the equa- 

 tion must be employed. It therefore becomes necessary to abandon the 

 values for the density of mercury and for standard gravity heretofore em- 

 ployed, which had the sanction of the International Meteorological Com- 

 mittee, in favor of the more recently determined values that have been 

 adopted by the International Bureau of Weights and Measures. 



The value adopted for A is 13.5951 grams per cubic centimeter;^ and 

 for (/o, 980.665 dynes. ^ 



By the use of these constants in the above equation we obtain 

 Pmb = 1-333224 B (millimeters), and 



Pm, = 'o^oIIIt ^ = >^3-86395 B (inches) 



ivhere B is the height of the barometer in the units indicated, after reduc- 

 tion to standard temperature and the standard value of gravity. 



Table 1 1 , Barometric inches to millibars. 



The argument is for o.oi inch. From O.OO to 2.49 inches the tabulated 

 values are given to the nearest hundredth of a millibar, so that by removing 

 the decimal one place to the right the value in millibars of every tenth inch 

 from 0.0 to 24.9 inches may be obtained to the nearest tenth of a millibar. 

 From 25.00 to 31.99 inches the tabular values are given to the nearest tenth 

 of a millibar. 



The first part of the table may be used as a table of proportional parts 

 for interpolation. 

 Example : 



To convert 23.86 barometric inches into millibars of pressure. 



From Table 11, 23.8 inches = 806.0 millibars 

 " " " .06 inch = 2.0 " 



23.86 inches = 808.0 millibars 



Table 12. Barometric millimeters to millibars. 



The argument is for each millimeter from I to 799, and the tabular 

 values are given to the nearest tenth of a millibar. 



This table may also be used to convert millibars into millimeters of 

 mercury. 



national meteorological and aerological conferences. It is 1,000,000 times greater than 

 that given in the Smithsonian Physical Tables, 6th cd., 1914, p. 346. The smaller 

 value is generally employed by physicists and chemists. See Marvin, Charles F. No- 

 menclature of the Unit of Absolute Pressure. Monthly Weather Review, 1918, 46 : 73-75. 



^ Chappuis, Recueil de Constantes Physiques, Soc. Fr. Phys., 1913, p. 139. Leduc, Trav. 

 et Mem., Bur. Int. Poids et Mes., xvi, p. 36, 1917. 



* Comptes Rendus des .Seances, Troisieme Conference Generale, p. 68. Trav. et Mem., 

 Bur. Int. Poids et Mes., xii, 1902. 



