OBSERVATIONS OF THE TOTAL SOLAR ECLIPSE OF 



MAY 29, 1 91 9 

 By C. G. abbot and A. F. MOORE 



The station was located at El Alto, on the rim of the canon in which 

 La Paz, Bolivia, lies. The approximate location of El Alto is 

 latitude, 16° 30' S. ; longitude, 4'' 33°^ W. ; altitude, 4,120 meters. 

 Although at a high altitude the sky is rarely free from clouds, but 

 very favorable conditions existed during the total and partial phases 

 of the eclipse. 



The Smithsonian Institution expedition to the eclipse consisted of 

 Dr. C. G. Abbot and Mr. A. F. Moore. Dr. Abbot photographed the 

 corona with two telescopes of eleven feet focus, and Mr. Moore 

 carried on pyranometer observations during the eclipse, as well as at 

 the same time on the day preceding, and at intervals during the night 

 preceding. The telescopes were mounted in a vacant hotel building 

 and the pyranometer was set up on top of a high stone fence, about 

 one hundred feet back of the hotel building. 



THE PHOTOGRAPHIC OBSERVATIONS 

 Owing to the shortness of the time available for preparation after 

 the expected arrival of the party at La Paz every possible arrangement 

 had been made in advance to set up the photographic apparatus 

 quickly. For this purpose each of the three boxes which contained 

 the apparatus was designed in form and construction so as to act 

 as a support to some part of the photographic outfit when filled with 

 stones and laid upon the floor of any room which might be found 

 available for the observations. Also, every detail of the apparatus 

 was carried without any dependence on such lumber or other 

 material as might ordinarily be available. It was very fortunate that 

 this was so, for the expedition was delayed so that the apparatus was 

 set up only two days before the eclipse. 



The briefness of the time available for preliminary tests was 

 unfortunate in one respect. Owing to the very low altitude of the 

 sun (only twenty minutes after sunrise) when the eclipse took place, 

 the refraction of the terrestrial atmosphere was continually changing 

 at the time, so that the apparent motion of the sun in the sky was 

 at a variable rate not agreeing with that which prevailed later in the 



Smithsonian Miscellaneous Collections, Vol. 71, No. 5. 



