PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



PHILOSOPHICAL SOCIETY 



82 1ST MEETING 



The 821st meeting was held at the Cosmos Club, October 11, 1919. 

 The meeting was called to order at 8 p.m. by President Humphreys, 

 with about 50 members and guests present. 



C. G. Abbot: Solar studies in South America. 



The author went by way of the Panama Canal to Chile, Bolivia, and 

 Argentina, returning by the same route. Slides illustrative of the 

 scenes along the route were exhibited, also slides showing the total 

 eclipse of the sun and measurements of the variation of the brightness 

 of the sky during the course of the eclipse phenomena as observed at 

 La Paz, Bolivia. The solar corona at the time of the eclipse proved 

 to be of a type intermediate between that of the maximum and mini- 

 mum period of sun spots and was especially grand on account of the 

 great number and extent of the streamers of the corona and the immense 

 prominence which cast a crimson glory over the whole. The point of 

 observation, at 14,000 feet above sea level, looked out upon a horizon 

 made up of snow-covered mountains about 20,000 feet high. The sky 

 was clear, and on the whole the phenomenon was the grandest of the 

 kind which the observers had ever seen. 



A conference was held in Argentina with the Chief and Chief Fore- 

 caster of the Argentine Weather Bureau, who explained the methods em- 

 ployed and the success of the results obtained in forecasting by the aid of 

 daily telegraphic reports of the variations of the sun as observ^ed at the 

 Smithsonian Institution station at Calama, Chile. They expressed 

 themselves as very sanguine in regard to the value of the solar radiation 

 work for this purpose. 



Several weeks were spent at the Smithsonian observing station at 

 Calama, Chile, where fortunately a new method of solar constant de- 

 termination was worked out which is based upon observations made with 

 the spectrobolometer, the pyrheliometer and the pyranometer at one 

 epoch of time. All these observations may be made simultaneously 

 by two observers within a period of about ten minutes and they are 

 sufficient to furnish means of computing the solar constant of radiation 

 which may be finished within two hours by one computer. Thus the 

 result is obtained with ten minutes of observing and two hours of 

 computing instead of three hours of observing and fifteen hours of com- 



III 



