468 



These fractions coincide as nearly as could be expected, and some of 

 them in a remarkable manner ; and are, so far, calculated to inspire con- 

 fidence in both the formulae compared. But it is necessary to test 

 them under other circumstances of temperature and moisture. 



Regnault, in order to test the formula of August modified by him- 

 self, made many experiments in which the aqueous vapour was ab- 

 sorbed from a certain volume of atmospheric air, and weighed, the 

 moisture of another portion of the same air being calculated, by the ap- 

 plication of the formula to the indications of the Psychrometer. He has 

 constructed a Table in which the fractions of saturation derived from 

 both sources are given. The following Table contains a number of his 

 determinations, converted into English temperatures, pressures, and 

 elasticities ; and beside each I have placed the fraction of saturation, 

 derived from the same data, by means of Apjohn's formula, with coef- 

 ficient 88. 



Table II. 



Dry Bulb, 

 Fahr. 



Wet Bulb, 

 Fahr. 



Barometer, 



Fraction of Satura- 

 tion by Weighing. 



Fraction of Satura- 

 tion by Apjohn's 

 Formula. Coef- 

 ficient 88. 



Fraction of Satura- 

 tion by August's 



modified Formula. 

 Coefficient -429. 



o 



65»25 



o 



51-15 



29-70 



0-344 



03-48 



0-337 



64-54 



52-98 



29-71 



0-438 



0-448 



0-438 



64-50 



54-51 



29-57 



0-496 



0-517 



0-507 



64-18 



46-88 



29-72 



0-193 



0-211 



0-197 



62-02 



50-11 



29-94 



0-377 



0-408 



0-396 



59-43 



49 14 



30-02 



0-420 



0-457 



0*417 



57-33 



45-61 



30-10 



0-362 



0-366 



0-356 



55-72 



47-96 



29-78 



0-506 



0-555 



0-551 



55-61 



48-90 



29-50 



0-597 



0-613 



0 609 



54-57 



45 -70 



30-10 



0-466 



0-484 



0-474 



48-90 



42-12 



29-02 



0-545 



0-559 



0-554 



44*89 



41*52 



29-48 



0-731 



0-753 



0-750 



In the above Table the fractions of saturation obtained by Apjohn's 

 and by August's modified formulae agree tolerably well with the weights 

 ascertained by Eegnault. Both formulae give fractions a little higher. 

 But the following Table will show that the two formulae disagree ma- 

 terially with the weights in the case of low temperatures and very 

 humid atmospheres : — 



