He was President of the American Association for the 

 Advancement of Science in 1849; was chosen President of 

 the United States National Academy of Sciences in 1868; 

 President of the Philosophical Society of Washington in 

 1871; and Chairman of 'the Light- House Board of 'the United 

 States in the same year; the last three positions he continued 

 to fill until his death. 



Professor jjlettrg made contributions to science in elec- 

 tricity, electro-magnetism, meteorology, capillarity, acous- 

 tics, and in other branches of physics ; he published valuable 

 memoirs in the transactions of various learned societies of 

 which he was a member ; and devoted thirty -two years of 

 his life to making the Smithsonian Institution what its 

 founder intended it to be, an efficient instrument for the 

 "increase and diffusion of knowledge among men." 



M. R. WAITE. 

 Chancellor of the Smithsonian Institution. 



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