194 



THE HYGIENE OF RESPIRATION 



Record temperatures and subtract the reading of wet bulb from 

 that of dry. 



By reference to table, find relative humidity corresponding to 



FIG. 107. Wet and dry bulb thermometers arranged for whirling (Psychrometer) 

 to get quick readings. 



air temperature as given by dry bulb thermometer, and to dif- 

 ference between readings of 2 thermometers. 



