60 



KITE WORK OF THE WEATHER BUREAU 



Nebr., 29 per cent ; Springfield, 111., 21 per cent, and Fort Smith, Ark., 

 12 per cent, the surface humidity' being the higher, except at Fort 

 Smith. At tiiirteen out of the entire seventeen stations the differ- 

 ence did not exceed 10 per cent, and at nine stations it was 5 i)er 

 cent or less. 



For obvious reasons, as the altitude increased, the relative humid- 

 ity decreased whenever the winds were from north to west, particu- 

 larly from the northwest, and increased with winds from east to 

 south, particularly with those from the east. When the kite was in 

 or near clouds, the humidity would almost invarialjh' rise, fulling 

 again when the kite was freed from cloud influence. 



Vapor pressures were expressed in i)ercentages obtaine<l by the 



formula %, '"p " representing the vapor pressure at an}' given altitude 



and ";)"" that ob.served simultaneously at the earth's surface. Tlie 

 mean thus oljtained was 59 per cent, ami there was a steady, though 

 by no means uniform, decrease with increase of altitude. The per- 

 centage at 1,500 feet was 82 and at 8,000 feet 44. The decrease was 

 most rai)i(l between 2,000 and 5,000 feet, where it averaged 9 percent 

 for each I.OIHJ feet. Tlic lowest percentage, 52, was found at Omaha, 

 Nebr., and the highest,. 77, at Pierre, S. Dak. 



A comparative statement of kite, balloon, and mountain observa- 

 tions is given below. In determining these results the records of 

 1,123 kite a.scensions were used. There were 4 balloon ascensions by 

 Hammon and 2 l)y Hazen. It is not known liow many observations 

 were made by Hann. 



Diinhintion of V<(})or ]'refi.inr>' irilh Allitwh' 

 Value of '' fur each respective 1,000 feet of altitmle 



< lijiraoter of oViservut ions. 



Kite 



Bftlloon (Hammond 



Hitlloon ( Hazel) ) 



Hiillooii ( Harm) 



MoniiUkin (Uann).... 



1,500 



2,000 



feet. 



feet. 



0.82 



0.78 



0.9r. 



0.90 



0.89 



0.83 



0.84 



0.80 



0.8.3 



0.81 



:{,000 4,000 

 feet. feet. 



5,000 

 feet. 



6,000 

 feet. 



7,000 

 feet. 



S.fMX) 

 feet. 



0.70 0.01 

 0.87 0.68 



0.52 

 0.44 

 n.f." 

 0.60 

 0.61 



0.49 

 0.59 

 0.46 

 0.54 

 0..58 



0.39 



0.44 



0.80 0.78 



0.44 

 0.41 

 0.55 





O.fiG 0.61 

 0.80 0.66 



1 



0..37 

 0.47 



Mean 

 feet. 



0.59 



0.75 

 0.70 

 0.60 

 0.66 



Differences in wind direction were indicated by the changes in the 

 azimuths of the kites. These showed that, as an almost unvarying 

 rule, the general directions above and at the surface were practi- 



