MEASURING OF AIR. 



435 



The following Tables i (a) to i (e) give the details of the 

 observations and reduction of the Hygrometer readings. These 

 reductions have been made by aid of the tables pul)lishcd by the 

 Smithsonian Institution. An Assman Hygrometer was used, 

 which draws a current of air over the wet and dry bulbs at a 

 uniform velocity. The upper portion of the tables gives the 

 observations and the lower portion the reduction. Table I (f) 

 gives the Summary. 



For the purpose of determining the mean temperature of the 

 intake air, the readings of the dry bulb of the Assman Hygrometer 

 have been taken in preference to those of the Thermometer 

 attached to the Barometer. These latter readings would be too 

 high on account of the proximity of the instrument to the observ- 

 ers and to the electric lights used for reading the instruments. 



REDUCTION OF HYGROMETER READINGS. 



Dry Bulb°F. = 61.0 = / 

 Wet Bulb°F. = 42.4 = t^ 



t - t, °F. = 18.6 

 Pressure of saturated aqueous vapour {t^) ^ 0.270 =: /^ 

 0.0003676 (t — t^) (1+ (t~t^) / 1571) =0.172:=/, 

 \'apour pressure (/^ — /., ) = 0.098 = / 



Pressure of saturated vapour ( / ) = 0.536 = F 



Relative Humidity. ==18.3 = f/F 



