associated with any brilliant discovery or achievement in astronomy, he has, nevertheless, secured as great a reputation as was ever gained by an American astronomer, and is quoted abroad as among the highest authorities in mathematical astronomy. Perhaps the secret lies in the unity of purpose which has characterized all his efforts. His special field has been that of "exact" astronomy—the prediction of the motions of the heavenly bodies from their mutual gravitation—the perfection of the tables and other data, from which the "Nautical Almanac" is prepared, in order that the navigator and surveyor may be enabled to find their positions by sea or land. When the late Admiral Davis founded the "American Nautical Almanac," some twenty-five years ago, the tables and other materials for its construction were extremely imperfect, but Prof. Newcomb's studies have all tended to their improvement.
Prof. Newcomb gained a European reputation while still a computer at Cambridge, by his paper "On the Secular Variations and Mutual Relations of the Orbits of the Asteroids." The question of the correctness of Olher's theory, that these bodies resulted from the explosion of a single planet, had never been decided, because no one had ever investigated the changes which their orbits had undergone in past ages. This was done in the paper we have mentioned, and it was shown that the orbits could never have intersected in a single point, unless they had in the mean while been deranged by some unknown cause.
Since his appointment in the navy his most considerable works, outside of his duties at the observatory, have been the "Investigation of the Orbits of the Two Outer Planets, Uranus and Neptune," accompanied by elaborate tables, which were at once adopted in all the nautical almanacs of Europe and America. In the preparation of these "tables," Prof. J. Henry, his kind and firm friend of now more than twenty years, took great interest, and gladly assisted him by supplying him with funds from the Smithsonian.
In 1867 the observatory published his "Investigations of the Distance of the Sun," leading to the value of the Solar Parallax now most generally adopted, namely, 8".848.
In 1870 he visited Europe to observe the total eclipse in the Mediterranean, and was everywhere received with the highest distinction in scientific circles.
He took an active part in procuring the great telescope for the Washington Observatory, and was in charge of it during the first year or two after its erection, investigating with it the satellites of his two favorite planets, Uranus and Neptune.
When Congress authorized the organization of parties to observe the late transit of Venus, Prof. Newcomb was appointed one of the commission to prepare the plans for those parties, and to arrange for the complete execution of those plans, after the return of those parties
