Died in 1867. Webster, J. W., Cambridge, Mass. (1). Died Aug. 30, 1850, aged 57. Died in June, 1882. Wheatland, Richard H., Salem, Mass. (13). Born April, 1832. Died July Wheatley, Charles M., Phoenixville, Pa. (1). Jan. 6, 1881. Born July 6, 1830. Died Died May 6, 1882. Born in March, 1859. Died White, Samuel S., Philadelphia, Pa. (23). Died Dec. 30, 1879. Whiting, Lewis E., Saratoga Springs, N. Y. (28). Born March 7, 1815. Died Aug. 2, 1882. Whitman, Wm. E., Philadelphia, Pa. (23). Whitney, Asa, Philadelphia, Pa. (1). Born 1874. Died in 1875. Dec. 1, 1791. Died June 4, Died in 1872. Whittlesey, Charles C., St. Louis, Mo. (11). 1870. Williamson, R. S., San Francisco, Cal. (12). Wilson, W. C., Carlisle, Pa. (12). Died April 15, Winlock, Joseph, Cambridge, Mass. (5). Born Feb. 6, 1826. Died June 11, 1875. Woodbury, Levi, Portsmouth, N. H. (1). Born Dec. 22, 1789. Died Sept. 4, 1851. Woodman, John S., Hanover, N. H. (11). 1871. Woodward, J. J., Washington, D. C. (28). Wright, John, Troy, N. Y. (1). Born in 1819. Died May 15, Wyman, Jeffries, Cambridge, Mass. (1). Born Aug. 11, 1814. Died Sept. 4, 1874. Yarnall, M., Washington, D. C. (26). Born in 1817. Died Jan. 27, 1879. Young, Ira, Hanover, N. H. (1). Died Sept. 14, 1858, aged 57. ADDRESS BY PROFESSOR C. A. YOUNG, THE RETIRING PRESIDENT OF THE ASSOCIATION. PENDING PROBLEMS IN ASTRONOMY. MR. PRESIDENT, LADIES AND GENTLEMEN OF THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE: THIRTY-SIX years ago this very month, in this city, and near the place where we are now assembled, the American Association for the Advancement of Science was organized, and held its first meeting. Now, for the first time, it revisits its honored birthplace. Few of those present this evening were, I suppose, in attendance upon that first meeting. Here and there, among the members of the association, I see, indeed, the venerable faces of one and another, who, at that time in the flush and vigor of early manhood, participated in its proceedings and discussions; and there are others, who, as boys or youths, looked on in silence, and listening to the words of Agassiz and Peirce, of Bache and Henry, and the Rogers brothers and their associates, drank in that inspiring love of truth and science which ever since has guided and impelled their lives. Probably enough, too, there may be among our hosts in the audience a few who remember that occasion, and were present as spectators. But, substantially, we who meet here to-day are a new generation, more numerous certainly, and in some respects unquestionably better equipped for our work, than our predecessors were; though we might not care to challenge comparisons as regards native ability, or clearness of insight, or lofty purpose. And the face of science has greatly changed in the meantime; as much, perhaps, as have this great city and the nation. One might almost say, that, since 1848, "all things have become new" in the scientific world. There is a new mathematics and a new astronomy, a new chemistry and a new electricity, a new geology and a new biology. Great voices have spoken, and have transformed the world of thought and research as much as the material products of science have altered the aspects of external life. The telegraph and dynamo-machine have not more changed the conditions of business and industry than the speculations of Darwin and Helmholtz and their compeers have affected those of philosophy and science. But, although this return to our birthplace suggests retrospections and comparisons which might profitably occupy our attention for even a much longer time than this evening's session, I prefer, on the whole, to take a different course; looking forwards rather than backwards, and confining myself mainly to topics which lie along my own line of work. The voyager, upon the inland sea of Japan, sees continually rising before him new islands and mountains of that fairyland. Some come out suddenly from behind nearer rocks or islets, which long concealed the greater things beyond; and some are veiled in clouds which give no hint of what they hide, until a breeze rolls back the curtain: some, and the greatest of them all, are first seen as the minutest speck upon the horizon, and grow slowly to their final grandeur. Even before they reach the horizon line, while yet invisible, they sometimes intimate their presence by signs in sky and air; so slight, indeed, that only the practised eye of the skilful sailor can detect them, though quite obvious to him. Somewhat so, as we look forward into the future of a science, we see new problems and great subjects presenting themselves. Some are imminent and in the way, they must be dealt with at once, before further progress can be made; others are more remotely interesting in various degrees; and some, as yet, are mere suggestions, almost too misty and indefinite for steady contemplation. - With your permission, I propose this evening to consider some of the pending problems of astronomy, those which seem to be most pressing, and most urgently require solution as a condition of advance; and those which appear in themselves most interesting, or likely to be fruitful, from a philosophic point of view. Taking first those that lie nearest, we have the questions which relate to the dimensions and figure of the earth, the uniformity of its diurnal rotation, and the constancy of its poles and axis. I think the impression prevails, that we already know the earth's dimensions with an accuracy even greater than that required by any astronomical demands. I certainly had that impression myself not long ago, and was a little startled on being told by the superintendent of our Nautical almanac that the remaining uncertainty is still sufficient to produce serious embarrassment in the reduction and comparison of certain lunar observations. The length of the line joining, say, the Naval observatory at Washington with the Royal observatory at Cape of Good Hope, is doubtful; not to the extent of only a few hundred feet, as commonly supposed, but the uncertainty amounts to some thousands of feet, and may possibly be a mile or more - probably not less than a ten-thousandth of the whole distance; and the direction of the line is uncertain in about the same degree. Of course, on those portions of either continent which have been directly connected with each other by geodetic triangulations, no corresponding uncertainty obtains; and as time goes on, and these surveys are extended, the form and dimensions of each continuous land-surface will become more and more perfectly determined. But at present we have no satisfactory means of obtaining the desired accuracy in the relative position of places separated by oceans, so that they cannot be connected by chains of triangulation. Astronomical determinations of latitude and longitude do not meet the case; since, in the last analysis, they only give at any selected station the direction of gravity relative to the axis of the earth and some fixed meridian plane, and do not furnish any linear measurement or dimension. Of course, if the surface of the earth were an exact spheroid, and if there were no irregular attractions due to mountains and valleys and the varying density of strata, the difficulty could be easily. evaded; but, as the matter stands, it looks as if nothing short of a complete geodetic triangulation of the whole earth would ever answer the purpose, a triangulation covering Asia and Africa, as well as Europe, and brought into America by the way of Siberia and Behring's Strait. It is indeed theoretically possible, and just conceivable, that the problem may some day be reversed, and that the geodesist may come to owe some of his most important data to the observers of the lunar motions. When the relative position of two or more remote observatories shall have been precisely determined by triangulation (for instance, Greenwich, Madras, and the Cape of Good |