SMITHSONIAN INSTITUTION 



Fig. I. — The desolate Mount Brukkaros, South West Africa, where the 

 Smithsonian operates for the National Geographic Society its solar radiation 

 station. The dwelling in foreground, the observatory beyond on the left. 



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I'lc. 2. — Air. Greeley observing the sun's heat with the silver-disk pyrheli- 

 ometer at the National Geographic station on Mt. Brukkaros, South West 

 Africa. 



