the institution is also secretary of this board and the principal executive officer.
Buildings.—The Smithsonian Institution is housed in two buildings the Norman, castlelike structure completed in 1855, and the huge one-story museum, to be noted below. The former is occupied as follows: The east wing contains the administration offices, comprising the rooms for the regents, the secretary, the editor, and other officers. A small library of reference books (thirty thousand volumes) occupies a part of the ground floor. The main central hall is filled with valuable collections in ornithology and conchology, including the Isaac Lea cabinet of shells. Above this, another large hall is devoted to prehistoric anthropology. The west wing contains ichthyological specimens, and a very beautiful collection of Crustacea, batrachia, and ophidia. In the south porch is a small group of instruments of research.
Correspondence.—The official and casual correspondence of the Smithsonian Institution is no insignificant part of its daily life. Letters are addressed to the Secretary by the most learned scholars of Europe as well as by the humblest seeker after truth living in the wilds of North America, and all receive consideration and respectful answers. Tens of thousands of letters are annually received and acknowledged. If inquiries are made which the Secretary and his aids can not immediately answer, the letters are referred to eminent specialists outside of the institution.
The official list of correspondents, embracing learned societies and men of science throughout the world, numbers twenty-four thousand (1894). For a great many years the responsibility of the official correspondence devolved on the chief clerk, Mr. William J. Rhees, who is now keeper of the archives of the institution.
The International Exchange Service.—The Board of Regents in 1851 established a system of international exchanges of the transactions of learned societies and of certain other classes of scientific works. The exchange extends also to specimens in natural history. In 1867 Congress imposed upon the institution the duty of exchanging official documents printed by order of either House, or by the United States Government bureaus, for similar works published by foreign governments.
This international exchange is of the greatest service to learned societies on both sides of the ocean, and to individual men of. science who avail themselves of its privileges; it involves a prodigious amount of well-directed labor, as shown by the fact that in the twelve months 1893 to 1893 over one hundred tons of books were handled; these comprised 39,500 packages and 31,850 Government documents sent out, besides 101,000 packages and 5,190 Government publications received.