380 S. A. Hill — Psychrometer and Condensing Hygrometer. [No. 4, 



Regnault got too low results by using his finally adopted formula in 

 dry states of the atmosphere, this was rather the effect of a high wind 

 than of the mere dryness of the air. 



The first practical conclusion to be drawn from the discussion of 

 these observations is that Regnault's modification of August's psychro- 

 metric formula is not likely to be improved upon, since it takes into ac- 

 count all the more important variables upon which the indications of the 

 instrument depend, except the uncertain one of wind movement, and 

 its constants have been correctly adapted to suit the condition of a 

 moderate breeze in the open air. The second is that, if we want the dry 

 and wet bulb thermometers to indicate the humidity correctly at times 

 when there is no wind, we should make arrangements to ventilate them 

 artificially at the moment of observation. This is not regularly done at 

 any of our Indian observatories. 



