67 



EXAMPLE I. 



What is the correction for refraction for an altitude of 8 5', the thermometer 

 standing at 50-0 and the barometer at 29*6 inches? 



Answer (by inspection) 6' 25" : 



and therefore, 



Apparent altitude . . . . = 8 5' 



Refraction 6 25" 



True altitude 7 58 35 



EXAMPLE II. 



What is the correction for refraction for the same altitude, the thermometer 

 tending at 44 and the barometer at 29-45 inches ? . 



Thermometer correction for altitude 8 5' = -f 6 

 Barometer ditto = 02 



Correction for both is = -(- 4 



Mean Refraction = 6 25 



.-.True refraction .. .... = 621 



O ' If 



Apparent Altitude . . . . . . = 850 



True refraction . . = 6 21 



True altitude . . 00 7 58 39 



