184 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 31 



BALLOON PYRHULIOMLTER. 



Figure 6. — Diagram of balloon pyrheliometer 



a. Blackened metal disk ; d d, flat-backed thermometer ; g h i, shutter ; f, clock rotating 

 shutter and photographic drum ; e, photographic recording drum ; n o, barometric ele- 

 ment ; r, windbreak. 



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Figure 7. — Record of automatic recording balloon pyrheliometer, July 11, 1914 



