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Rh regarding the sun which could not be ascertained at a lower altitude. Early in 1887 he became assistant secretary of the Smithsonian Institution, and a few months later he was appointed secretary, which position he is holding at the present time (1906). Although the duties of this office have required a large part of his time and effort he has never discontinued his scientific investigations. Among the important public services which he has rendered while connected with the institution are the establishment of the National Zoological Park and of the Astrophysical Observatory.

In authorship Professor Langley has done work that is of great and permanent value, although most that he has written has been on scientific subjects treated technically and therefore has not been widely read. Among his principal works of this kind are "Experiments in Aerodynamics" and "Internal Work of the Wind," both of which were published by the Smithsonian Institution. Many smaller treatises have been printed in the memoirs of various learned societies in England, France, and Germany as well as in the United States. In "The New Astronomy" Professor Langley has departed from a technical style and has written a book which presents the facts of astronomical science in a most attractive manner for popular reading. Occasional articles in the "Atlantic," the "Century," and other magazines, have been written in a popular style and have been very favorably received.

Professor Langley has invented several valuable scientific instruments; but as he has preferred to give his fellow workers the full benefit of his labors in this important field he has never taken out a patent. One of the best known of these inventions is the "bolometer," which is used in the study of certain characteristics of the sun and which is so greatly superior to any other instrument for the purpose that it has been adopted at all the leading physical laboratories of the world. Another invention, which has not yet been perfected, is that of the aerodrome, or "flying machine." Professor Langley was the first to construct (in 1896) a machine which, supported only by mechanical power, made repeated flights for considerable distance.

Among the honorary degrees which Professor Langley has received are Ph.D. from Stevens Institute of Technology; LL.D. from Harvard, Princeton, Yale, Michigan and Wisconsin universities; D.C.L. from Oxford, and Sc.D. from Cambridge, England. He is a