NO. S 



SMITIISOMAN l-..\l'l.()UATU)NS. Kjl,^ 



«7 



All the balloons carrying ])yi'li«^'li<>in«-^ltM-s were fortunately re- 

 covered, and in one instance the flight reached the altitude of about 

 Vvooo meters, or 108,000 feet. The registering pyrhelionieters be- 

 haved very well with the excei)tion that their temperature sunk lower 

 than was expected, so that in each case the mercury in the stem of the 



Fk; 80— Observing station of Astrophysical Observatory 

 on Mount Wilson wiili new tower telescope. Photograph by 

 Abbott. 



thermometers was frozen at an altitude of from 40 to 50 thousand 

 feet, and therefore their records did not extend as high as the flights 

 of the balloons. Xevertheless these measurements are obtained at 

 altitudes above the highest clouds, and where the water-vai)or and 

 (lust of the atmosi)here is almost inappreciable. The results reached 

 do not difl:'er from what would l)e expected in view of the value of 



