EXAMPLE. Let the temperature of the air be 

 70 F., and the dew point the same. Then op- 

 posite the temperature you have the weight of a 

 cubic foot of vapor 8. 392 grains. 



But if the temperature of the air be different 

 from the dew-point, a correction is necessary to find 

 the exact weight. 



EXAMPLE. Suppose the dew- point 'be 70 F., as 

 before, but the temperature of the air in the shade 

 be 80, then the vapor lias suffered an expansion due 

 to an excess of 10, which requires a correction. 



We find in the table of corrections for 10 is 

 1.0208. 



Then divide 8.392 grains at the dew-point, viz., 

 70 by the correction, corresponding to the degrees 

 of absolute dryness, viz. , 10, and you have the 

 actual weight of vapor existing. 



8.3920 



EXAMPLE. 8.221 grains existing, which 



1.0208 



substracted from the weight of vapor, correspond- 

 ing to the temperature of 80 F., gives the number 

 of grains required for saturation at that tempera- 

 ture. 



EXAMPLE. 11.333 gr. at the temp, of 80 F. 

 8.221 gr. contained in the air. 



3.112 gr. required for saturation. 

 To find the relations of these conditions on the 

 natural scale of humidity [complete saturation 

 being i.ooo], divide the weight of vapor at the dew 

 point by the weight at the temperature of the air, 

 125 



