Tables 174, 175. 



DENSITY OF AIR FOR DIFFERENT PRESSURES AND HUMIDITIES. 



TABLE 174. — Values ol '' , Irom /i = 1 to // = 9, lor the Computation of Diflerent Values ol the Ratio 

 760 



of Actual to Normal Barometric Pressure. 



This cives the density of air at pressure A in terjns of the density at normal atmosphere pressure. When the air 

 contains moisture, as is usually the case with the atmosphere, we have the following equation for the dry air 

 pressure : // = B — o.378<', where e is the vapor pressure, and B the observed barometric pressure corrected for 

 temperature. When the necessar\' observations are made the value of e may be taken from Table 170, and then 

 0.378^ from Table 172, or the dew-point may be found and the value of o.n'&e taken from Table 172. 



Examples of Use of the Table. 



To find the value of — when h ^ 754.3 

 760 



h := 700 gives .92105 



50 " .065789 



4 " .005263 



.3 " .000395 



754-3 



.992497 



To find the value of — when h =: 5.73 

 760 



A = 5 gives .00657S9 

 .7 " .0007895 

 .03 " .0000395 



5-73 



.0074079 



TABLE 175. —Values of the logarithms of -^ for values of /< hetween 80 and 340. 



Smithsonian Tables. 



162 



