14 



Relative 



atures. The rate of increase forms a curve, as shown in the diagram 



annexed, but increasing in 

 percentage more slowly as 

 the temperature is high. 

 These curves are higher 

 when the wet and dry bulb 

 thermometers are nearer 

 alike, and grow smaller at a 

 regularly decreasing rate as 

 the differences between in- 

 struments increase. 



60. At all temperatures, 

 the relative humidity dimin- 

 ishes in percentage as the 

 difference between the in- 

 struments increases, as we 

 sec by the descending curves 

 in Figure 4, but not at uni- 



3. Relative Humidity at different Tempera- form rates, as WC see that 

 tures the difference between wet and dry Bulbs 



being constant. these lines are curves. The 



degrees marked on these 

 curves from to 100 are 

 those of temperature in the 

 open air. 1 



(1) The numerical statements 

 from which this and the preced- 

 ing figures are constructed will 

 be found in a volume of meteor- 

 ological tables prepared by Pro- 

 fessor Guyot, and published by 

 the Smithsonian Institution for 

 the use of its observers, at the 

 time when the former system 

 of voluntary meteorological ob- 

 servation was in operation. The 

 limits of this volume do not ad- 

 mit of their insertion in detail, 

 nor of a statement of the 



4. Relative Humidity at fixed Temperatures, P rinci P ]es U P on whidl tht '>' are 

 the dillorenee between wet and dry Bulbs bein" based. 



variable. 



