136 



MILLIKAN— METEOROLOGICAL WORK 



ing temperature of the surrounding air, the changing size of the 

 balloon and consequent changing tension of the rubber envelope, the 

 changing temperature of its interior because of the absorption of 

 the sun's rays, the diffusion of hydrogen through its walls, etc., it 

 is one of the most striking facts to be found anywhere in the annals 



c", Aberdeen Pr«i/i,,n2 Ground, Mci, 



tinv^orm Rate o| Ascent 



70 80 



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



of empirical science that these balloons rise to great heights without 

 deviating appreciably from the simplest possible law of ascent, 

 namely, that of constant speed. Graphs Nos. i, 2, 3, 4 and 5 show 

 beautiful examples of this constancy. Graph No. 6 shows a kink 

 at about 5,500 meters, which is presumably due to a descending 

 current struck at that altitude. Graph No. 7 shows a balloon fol- 

 lowed to a height of 20,000 meters where it apparently developed a 



