142 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1916. 



and he later developed *and built the first man-carrying aeroplane 

 capable of sustained free flight. Langley's success as a pioneer in 

 aviation was commemorated on the Column of Progress at the 

 Panama-Pacific International Exposition by a tablet bearing the 

 inscription : " To commemorate science's gift of aviation to the world 

 through Samuel Pierpont Langley, an American." 



It was Prof. Langley who, in 1869, inaugurated a general system of 

 standard-time distribution to various cities and railroads, a sj^stem 

 which in 1885 had extended to 4,713 miles of railroad and is now 

 universal throughout the country. 



He devised that most delicate instrument — the bolometer or elec- 

 trical thermometer — by which changes of temperature of less than 

 the hundred-millionth of a degree centigrade are measured, and by 

 special installation differences in temperature amounting to one- 

 billionth of a degree can be detected. Langley's investigations in 

 radiation include {a) the distribution of radiation over the sun's 

 surface and in sun spots, (&) the solar energy spectrum and its 

 extension toward the infra red, {c) the lunar energy spectrum and 

 the temperature of the moon, {d) spectra of terrestrial sources and 

 determination of hitherto unmeasured wave lengths, and {e) the 

 absorption by the earth's atmosphere of the radiation of the sun and 

 the determination of the solar constant of radiation. In each of 

 these lines of research important discoveries were made by Langley, 

 and since his death the work has been greatly advanced through the 

 present director of the Smithsonian Astrophysical Observatory, Dr. 

 Charles Greeley Abbot. 



It was during the administration of Secretary Langley that the 

 National Zoological Park, largely the outgrowth of investigations 

 on living animals under the direction of Assistant Secretary G. 

 Brown Goode, was founded, and during this period there was begun 

 the erection of the present great structure for the natural history 

 collections of the National Museum, a building planned under the 

 direction of Assistant Secretary Eichard Rathbun, who had made 

 careful studies of the principal museums of the world. 



Charles Doolittle Walcott, the present Secretary, a geologist and 

 paleontologist, began his administration as Secretary of the Institu- 

 tion in 1907, having been connected with the Museum as an honorary 

 officer of the department of paleontology since 1882. From 1888 

 to 1907 he held various positions in the United States Geological 

 Survey, being its director from 1894 to 1907. His special study has 

 been Cambrian geology and paleontology, and he has recently suc- 

 ceeded in bringing to light evidences of algal life in the pre-Cam- 

 brian Algonkian sediments, as also the discovery of most delicate 

 examples of fossil holothurians and meduste in Middle Cambrian 



