NO. 12 DETERMINATION OF AQUEOUS VAPOR ALDRICH 3 



of the equipment for this work was brought from Burro Mountain 

 near Tyrone, N. Mex., where for some years the Smithsonian 

 Institution maintained a high-altitude solar station. 



The circumstances of a Smithsonian solar field station operating at 

 a wet, sea-level location is unique. The only previous spectrobolo- 

 metric set-up at sea level was the original Washington equipment of 

 some 40 years ago, which Fowle used in his precipitable-water studies 

 above mentioned. The Miami set-up thus offered opportunity to check 

 the correctness of Fowle's precipitable-water curve. 



■%--->-^ 



Ms 





Fig. 2. — Path of beam. L, light source; Mi, Mi, concave mirrors, i-m. focus; 

 C, coelostat plane mirror; S, slit; B, bolometer. 



We originally planned to do this in June 1948, at which time of 

 year there is normally a maximum of atmospheric humidity. Unavoid- 

 able delays occurred, however, and holographs were not obtained until 

 January 1949. The following summarizes the work: 



A 500-watt projection lamp was placed in the focus of a 9-inch- 

 diameter aluminized mirror of i meter focal length. The assembly 

 was mounted on a movable table in the field adjoining the station 

 building. The approximately parallel beam from the mirror fell upon 

 the second mirror of the coelostat and from there passed through the 

 spectrobolometer, housed in the station building (fig. 2). 



In Smithsonian solar-constant observations, standard conditions 

 of slit width, bolometer strip width, and time of swing of the gal- 



