MR. W. N. SHAW ON HYGROMETRIC METHODS. 



LSI 



and the dew-point was computed from them by APJOHN*S formula,* by GLAISHER'S 

 factors, and by AUGUST'S theoretical formulat supplied with RKGNAULT'S values of the 

 constants occurring therein and adapted to English units. The thermometers were 

 either a pair with small pea bulbs or a pair of CASSELLA'S Kew pattern, with small 

 spherical bulbs. Particulars are given with reference to the verification of their indi- 

 cations. 



The wet bulbs were exposed either (I) in a thermometer shed, i.e., " in a frame with 

 one or two cross bars (generally protected by wire netting at back and front) under a 

 thatched shed open on all sides to the wind," or (2) by the " sling " method. For the 

 Upper India series the bulbs were covered with a single thickness of old thin calico. 

 A water bottle was placed two inches to the side of the bulb with the water level a 

 quarter-inch below it, and communication was made by a well-washed lamp-wick of 

 some dozen threads of coarse yarn. 



The dew-point instrument was CASSELLA'S form of REGNAULT. 



Assuming the direct dew-point determinations to be correct, the following are the 

 errors shown by the several computations : 



83 ' 30' 



t/- 



32) 



,/ - 



'fc. 0'>: 



