THE RADIATION OF THE SUN. 



By C. G. Abbot,' 

 Director of tlic Astrophysical Observatory of the Smithsonian Institution. 



[With 4 plates.] 



The sun presents many interesting aspects. Although controller 

 of the solar system, an object rich with beautiful and curious features, 

 the nearest of the fixed stars, and typical of a large class among them, 

 tlie sun also has a still greater claim on human interest as the foun- 

 tain of heat, light, and life upon the earth. It is this latter aspect 

 which we shall consider mainly, still further confining our attention 

 almost wholly to work done under the auspices of the Smithsonian 

 Institution. 



Wlien James Smithson died in Genoa m 1829 he left his estate, 

 subject to certain conditions, "to the United States of America, to 

 found at Washington, under the name of the Smithsonian Institution, 

 an Establishment for the increase & diffusion of knowledge among 

 men." On May 9, 1838, by decree of the English Court of Chancery, 

 the Smithson bequest, amountmg to about $500,000, was adjudged 

 to the United States. By the act of establishment in 1846 the con- 

 trol of the Smithsonian Institution is vested by Congress in a Board 

 of Regents, comprismg the Vice President and the Chief Justice of the 

 United States, tliree Senators, tliree Representatives, and six private 

 citizens. In the years that have elapsed the Smithsonian private 

 funds have increased by gifts and economy to nearly $1,000,000. 

 For many years the institution has administered the annual con- 

 gressional appropriations for the support of the National Museum, 

 National Zoological Park, Bureau of American Ethnology, Astro- 

 physical Observatory, Bureau of International Exchanges, and 

 International Catalogue of Scientific Literature. The immediate 

 administration is m the hands of the secretary of the Board of 

 Regents, at present Dr. C. D. Walcott, the fourth of the secretaries. 



Dr. S. P. Langley, the tlih'd secretary, a distinguished American 

 astronomer, founded m 1890 the Astrophysical Observatory of the 



• Reprinted with revision and addition from Science Conspectus, Boston, vol. 2, No. 5, April, 1912. 

 Illustrations ui part from "The Sun," by permi&sion of D. Appleton & Co. 



153 



