138 



MILLIKAN— METEOROLOGICAL WORK 



the pressure is about a third of an atmosphere. This means that 

 the ascensional force must be entirely independent of temperature 

 and pressure.^ For the speeds with which these balloons ascend, 

 namely, about three meters a second, the resistance to motion must 

 be directly proportional to the density of the air and experiment 



I r 



L 



Akefdeerv Prot/tnig Crfo and, W <k 



^"October" 2 3, Iq lit " l0:6'0Z"i^7~'"^ 



Ho A 





^' 



L° r ■ M i- 



[--i:-4--J.-^ 



Ith ii.|br#; aate IdI 'Ascent* 



-U^ 





6 10 IS 2U 25 30 35 « 4S SO SS SO <S 



Time (Minutes) 



Uniform rate of ascent of pilot balloon up to 8,ooo meters. 



shows it to be nearly proportional to the cross section of the balloon, 

 that is, to the square of the radius. This makes the resistance vary 



1 For if /i, di, Vipiti represent ascensional force, density, volume, pressure 

 and temperature at the surface of the earth, and f-2, d-, Vi, p2, ti, the correspond- 

 ing quantities at any given elevation, then since dJdi=^Vi/v-.=^ pJjpit. (i) 

 and fJf2^=Vidi/Vid2 (2) there results from a combination of i and 2, 

 fjf., = vAJvid-, = p;UlpxU X p^hlp-^x — I. 



