Absolute and Relative Humidity. 



13 



temperature, the amount is 

 and dry bulbs is greatest, 

 and it increases as tliese dif- 

 ferences become less, as we 

 see by Diagram 2, where 

 the lines descend from left 

 to right. The rate of de- 

 scent is similar at difi'erent 

 temperatures, as we see the 

 descending lines are parallel, 

 but they become nearer to- 

 gether as the temperature is 

 less. In this diagram, the 

 degrees on the oblique lines 

 are those of temperature in 

 the open air. If we meas- 

 ure the vertical distances be- 

 tween these oblique lines, we 

 would have a series of num- 

 bers increasing at a gaining 

 rate, which might be shown 

 by a curve something like 

 those of the preceding figure. 

 59. The Relative Humid- 

 ity. This is the percentage 

 of saturation, 100 being com- 

 plete saturation, as in a fog 

 (when the air can hold no 

 more moisture in invisible 

 form), and being com- 

 plete dryness. In our cli- 

 mate, we never find the air 

 absolutely dry without arti- 

 ficial means. The degree of 

 rela,tive humidity also de- 

 pends on the temperature, 

 and with a given distance 

 between wet and dry bulbs, 

 it is greatest at high temper- 



least when the difierence between wet 



1. Absolute Humidity at different Tempera- 

 tures, the JJiffopenee between wet and dry Bulb3 

 being constant. 



2. Absolute Humidity at fixed Temperatures, 

 the Difference between wet and dry Bulbs being 

 variable. 



