SAMUEL PIERPOXT LAxVGI.EY. I^ 



and the clearness of his st\le in presenting them attracted attention 

 far and wide. 



In the autumn of 1886 he was invited to the post of Assistant 

 Secretary of the Smithsonian Institution. In the invitation Pro- 

 fessor Baird, the Secretary at that time, assured him that, while 

 in his new post he would be expected to take charge of the 

 foreign and domestic exchanges, the library, and publications, 

 fully half of his time might be employed, to use Professor Baird's 

 own words, in "keeping up those original researches at Allegheny 

 Observatory which have already secured for you so much distinc- 

 tion in the scientific world." The invitation was accepted, and after 

 the death of Professor Baird, in August, 1887, ^^r. Langley was 

 elected by the Board of Regents Secretary of the Smithsonian 

 Institution. 



From the beginning of his life in Washington he gave especial 

 thought to the exchange service, the library, and the publications, 

 and ever retained a deep interest in these. To his mind, the ex- 

 change system was a main means of carrying out Smithson's be- 

 quest "for the diffusion of knowledge among men," and the publica- 

 tions were no less essential in accomplishing the founder's purpose 

 of "increasing knowledge." Noteworthy, especially, is the fact, 

 also, that Doctor Langley exerted himself constantly to see that the 

 reports were, as far as possible, free from unnecessary technical 

 terms and prepared in a language which could be understood by 

 every man of ordinary education and intelligence. 



Plis activities in behalf of the Institution were extended in many 

 ways, but he evidently felt that, apart from these, his main function 

 was to "increase knowledge" in the new department to which his 

 special astronomical researches had been mainly devoted. To this 

 end he established, under the direction of the Smithsonian Institu- 

 tion, an astrophysical observatory, the means for that purpose being 

 due, first, to the generosity of the late Jerome H. Kidder and of Mr. 

 Alexander Graham Bell, and later to appropriations by Congress. 

 The sum required was not a heavy burden on the public purse, but 

 after a few years, a question as to the usefulness of this observatory 

 having been raised in Congress, a committee was appointed to ex- 

 amine and report upon it. This committee communicated with the 

 foremost men of science in our own country and in Great Britain, 

 who were entitled to pass judgment on Doctor Langley 's work. 

 The expressions of these eminent astronomers were uniformly 

 favorable, and can best be summed up in a single declaration by 

 Sir William Thompson, now Lord Kelvin, that in the special and 



