ON August 22, the centenary of the birth of Samuel Pierpont Langley will be commemorated at the Smithsonian Institution, Washington. Langley was secretary of the Institution from 1887 until 1906; it was there he made his valuable investigations in aeronautics and to him was due the inauguration of both the Astrophysical Observatory and the National Zoological Park, which, like the United States National Museum and the Bureau of American Ethnology, are integral parts of the Institution. Much of his experimental apparatus is preserved in the Museum, and it has accordingly been arranged for a special exhibit devoted to his activities and honours to be unveiled on the hundredth anniversary of his birth. The exhibit is being arranged by Mr. T. T. Belote, curator of the Division of American History, and it will ultimately be one of four recalling his own work and that of his two predecessors, Joseph Henry, who was secretary from 1846 until 1878, and Spencer Fullerton Baird, who held the office from 1878 until 1887, and of his successor, Charles Doolittle Walcott, who was secretary from 1907 until 1927. It is also intended to direct attention to Langley's work in the Press, and to publish a special memoir of him containing some extracts from his writings.