30 SMITHSONIAN MISCELLANEOUS COLLECTIONS. 



like the late James E. Keeler, director of the Lick Observatory, 

 was an achievement of which any man might well be proud. 



While much of the work of the Astrophysical Observatory has 

 consisted in repeating and extending the earlier work of Lang- 

 ley, many new problems have been undertaken. A matter in which 

 he was greatly interested during the last years of his life was the 

 variation, if any, in the solar constant. This means possible changes 

 in the heat of the sun itself, which from observation with the bolo- 

 meter appeared to take place rapidly and irregularly, and to be real 

 and not due to changes in the atmosphere of the earth. It is diffi- 

 cult to estimate the commercial and industrial importance of the 

 effect of such changes, if they exist. The pecuniary value of a study 

 of them, if it led to a means of determining their laws so that they 

 could be foreseen, would be almost incalculable. 



The work of Langley may be summed up as that of an eager 

 searcher after truth, a careful and persevering investigator, and one 

 whose life was directed to the extension of human knowledge, not 

 only in lines of theoretical interest, but in those which, if successful, 

 would have the utmost practical value. 



LANGLEY'S CONTRIBUTIONS TO AERIAL N.WIGA- 



TION. 



BY OCTAVE CHANUTE. 



The Chief Justice : I will now introduce, my fellow-citizen, the 

 very distinguished engineer, Mr. Octave Chanute, of Chicago. 



yir. Chanute : Mr, Chief Justice, ladies and gentlemen : I have 

 been asked to refer briefly to the late Secretary Langley 's contribu- 

 tions to aerodynamics. 



Doctor Langley said that the subject of flight had interested him 

 as long as he could remember, but that it was a communication read 

 at the Buffalo meeting of the American Association for the Advance- 

 ment of Science, in 1886, which aroused his then dormant interest 

 in the subject. The explications of flight then given were so evi- 

 dently erroneous and there were so many conflicting theories on the 

 subject, that Langley determined to find out for himself, and in his 

 own way, what amount of mechanical power was requisite to sus- 

 tain a given weight in the air and make it advance at a given speed ; 

 for this seemed to him an inquiry which must necessarily precede 

 any attempt at mechanical flight, which was the very remote aim of 

 his efforts. Up to that time there had been a vast amount of specu- 



