224 ABSOLUTE HUMIDITY OR ELASTIC FORCE OF VAPORS. 



Absolute Ilumidity or elastic force of vapor, expressed in English inches, of mercurial column 

 at each tenth degree, from — 30^ to lUO" Fahrenheit, the differences between Thermometers 

 being as shown by the left-hand column. 



It will be seen that tbese numbers icoiease from left to right, aud 

 from below upwards. The rate of increase horizontally, that is to say, 

 with a constant difference between wet and dry bulb thermometers, (bat 

 ranging through all temperatures of the air from —20 to +100°), may be 

 shown by a curve, as in the left-hand drawing, where the range for 0°, 

 10°, and* 20° of difference is separately shown. It is seen to be a rapidly 

 gaining rate, nearly regular, and much like a geometrical progression. 



Absolute linmidity at difforent temperatures, the 

 difference between wet aud dry bulba being cou- 

 staut. 



Absolute hniuidity ftt fixed temper.atnres, the dif- 

 ference between wet and dry bulbs being vari- 

 able. 



The formulae do not strictly apply to high temperatures, but for the 

 common range, the rate of increase is very regular. But if we follow 

 any of the vertical columns downward, we observe a falling off which 

 becomes less as the heat is greater, the common difference being from 

 0.011 to 0.014. If this decrease be drawn in a diagram, it will api)ear as 

 iu the right-hand drawing, where the columns from 0° to 100° are rep- 



