Sumner, William G. The Conquest of the United States by Spain. Boston: Dana, Estes & Co. Smithsonian Institution: Doan, Martha. Index to the Literature of Thallium. Pp. 26; Proceedings of the United States National Museum. Index to Vol. XXI. United States Commission of Labor: Thirteenth Annual Report. Hand and Machine Labor. Two volumes. Pp. 1604. United States Geological Survey: Nineteenth Annual Report. Part I. Director's Report, including Triangulations and Spirit Levelings. Pp. 422, with map; Part IV. Hydrography. Pp. 814; Part VI. Mineral Resources of the United States. By David T. Day. Two volumes. Pp. 651 and 706.--Monographs: Vol. XXIX. Geology of Old Hampshire County, Massachusetts. By B. K. Emerson. Pp. 790, with maps; Vol. XXXI. Geology of the Aspen Mining District, Colorado. By J. E. Spurr. Pp. 260, with an Atlas of thirty sheets; Vol. XXXV. The Later Extinct Floras of North America. By J. S. Newberry. A posthumous work, edited by Arthur Hollick. Pp. 295, with 68 plates.--Maps and Descriptions of Routes of Exploration in Alaska in 1898. Pp. 138, with envelope containing ten maps. Young Men's Christian Association, Educational Department: Annual Report for 1899. Pp. 70; Prospectus for 1899 (July 1, 1899 to July 1, 1900). Pp. 112; Fourth International and other Exhibits. Awards of Merit. Pp. 24; The Present Status of Our Educational Work. By Frederic B. Pratt. Pp. 5. Fragments of Science. =Officers of the American Association for 1900.=--The American Association, at Columbus, Ohio, elected as president for the next meeting, which is to be held in New York city, June 25 to 30, 1900, Prof. R. S. Woodward, of Columbia University. The vice-presidents-elect are: Section A (Mathematics and Astronomy), Asaph Hall, Jr., of Ann Arbor, Mich.; Section B (Physics), Ernest Merritt, of Ithaca, N. Y.; Section C (Chemistry), James Lewis Howe, of Lexington, Va.; Section D (Mechanical Science and Engineering), J. A. Brashear, of Pittsburg, Pa.; Section E (Geology and Geography), J. F. Kemp, of New York city; Section F (Zoölogy), C. B. Davenport, of Cambridge, Mass.; Section G (Botany), William Trelease, of St. Louis, Mo.; Section H (Anthropology), A. W. Butler, of Indianapolis, Ind.; Section I (Economic Science and Statistics), C. M. Woodward, of St. Louis. The permanent secretary is L. O. Howard, United States Entomologist, Washington, D. C.; General Secretary, Charles Baskerville, of Chapel Hill, N. C.; Secretary of the Council, William H. Hallock, of New York city. The sectional secretaries are: Section A, W. M. Strong, of New Haven, Conn.; Section B, R. A. Fessenden, of Allegheny, Pa.; Section C, A. A. Noyes, of Boston, Mass.; Section D, W. T. Magruder, of Columbus, Ohio; Section E, J. A. Holmes, of Chapel Hill, N. C.; Section F, C. H. Eigenmann, of Bloomington, Ind.; Section G, D. T. McDougal, of New York Botanical Garden; Section H, Frank Russell, of Cambridge, Mass.; Section I, H. T. Newcombe, of Washington, D. C. Treasurer, R. S.