OF THE UNITED STATES ARMY. 



141 



When, however, the weight and inflation of the balloons are 

 varied, as they must be in practice, since the balloons vary in weight 

 from twenty to thirty-five grams, and since it is convenient also to 

 vary the filling according as low altitude or high altitude wind-data 



;j : I 



No. 



Col lea'e ■^to^tlan; !TV]i:a.P"i" 



July Ifc. Iq\ a _3":_03_p.m. i 



E Kceptiokally. Kig hi. As ee ns-i il 



CS so 73 100 125 ISO " !76 200 



TifttCAVmuTt?) _ ■ .^^ 



Uniform rate of ascent of pilot balloon up to 20,000 meters where balloon 



sprung a leak. 



are desired, it is found that no accurate formula can be found for 

 computing the speed in terms of the ascensional force, the weight 

 to be lifted, and a single invariable constant. For approximate 

 work, however, the one-theodolite method, because of its conve- 

 nience and because of the impracticability of measuring an accurate 

 base line at the front, is much in use, and one of the advances made 

 in the meteorological w'ork of the army during the past year has 



