ACADEMY 0, SCONCES.] BIOGRAPHY. 5 



In the volumes of Astronomical and Meteorological Observations Made at the United 

 States Naval Observatory, Washington, in the years 1861 to 1S70, inclusive, one finds abundant 

 evidence of Newcomb's great energy in using the instruments for which he was responsible, in 

 reducing the observations and in the prompt publication of the results. The same volumes 

 reveal his breadth of view and power, in a half dozen comprehensive papers, on the latitude 

 and longitude of the United States Naval Observatory, on the distance of the sun and the 

 elements which depend upon it, on the new transit instrument (a description), on the positions 

 of fundamental stars deduced from Washington observations made between 1862 and 1867, on 

 the right ascensions of the equatorial fundamental stars and the corrections necessary to reduce 

 the right ascensions of different catalogues to a mean homogeneous system, etc. 



Prof. Newcomb was detailed to observe the total eclipses of the sun at Des Moines, Iowa, 

 in June, 1869; at Gibraltar in December, 1870; and at Separation, Wyo., in July, 1S78. 3 He 

 was especially interested in determining the relative positions of the sun and moon, as indicated 

 by the times of the contacts of the lunar and solar images, by the durations of the eclipses, and 

 (in Iowa and in Wyoming) by the observed north and south limits of the shadow path. The 

 eclipses at Des Moines and at Separation were successfully observed, but the value of the 

 Gibraltar expedition was largely destroyed by the presence of clouds during the critical parts of 

 the eclipse period. 



At about this time Prof. Newcomb realized that the discrepancies between the observed 

 positions of the moon and the positions as predicted in Hansen's tables for the moon had become 

 a serious matter, and at his request it was arranged that he should be relieved from the duty 

 of making observations, and from other observatory work, in order to conduct an investigation 

 of the moon's motion, though at the request of the superintendent he retained his position on 

 the observatory staff. The lunar problem developed into the leading work of his life ; it received 

 his best efforts during many of the years 1870 to 1909. 



The devoting of the resources of the Naval Observatory to the determination of star posi- 

 tions and to the special needs of the Navy Department led naturally to the neglect of that side 

 of astronomical investigation which requires powerful telescopes. This fact was called to the 

 attention of the superintendent of the observatory by Prof. Newcomb in 1868, and again in 

 1869, with the recommendation that the observatory procure a refracting telescope as large 

 as the then celebrated maker, Alvan Clark, would undertake to construct. These recommenda- 

 tions led ultimately to the appropriation of $50,000 for the purpose by the Congress of 1870-71. 

 It was decided by Mr. Clark and the observatory authorities that the telescope should be a 

 refractor of 26-inch aperture. Prof. Newcomb tested the object glass in Cambridge in the 

 summer of 1873, and the records show that the first observations made with the telescope 

 finished and mounted in the Naval Observatory were of Neptune's satellite, by Newcomb, on 

 November 20, 1873. He remained in charge of" the instrument until May, 1875. In that 

 period he made many measures of the positions of the satellites of Uranus and Neptune, as a 

 basis for determining more accurately the masses of the two planets, in order to facilitate his 

 work of reconstructing the tables of the motions of the planets; many observations of the 

 satellites of Saturn; and a few observations of occultations and of double stars. 



Prof. Newcomb was prominently associated with the plans for observing the transits of 

 Venus over the sun in the years 1874 and 1882, to obtain an improved value of the distance 

 between the earth and the sun. He inaugurated the proposal at the April, 1870, meeting of 

 the National Academy of Sciences — the first annual meeting following his election to mem- 

 bership — by reading a paper * concerning the coming transits, and by introducing a resolution 

 calling for the appointment of a committee to consider and report upon the subject. This 

 resulted, in 1871, in the establishment of the Transit of Venus Commission, of five members, 

 including Prof. Newcomb and Prof. Harkness. Newcomb was elected secretary of the commis- 

 sion. The co mmi ssion gave to the subject the serious consideration demanded by its character 



3 At this time Newcomb was superintendent of the Nautical Almanac and not officially connected with the Naval Observatory, but the expe- 

 dition was under the auspices of the Observatory and the report upon the observations was addressed to the Superintendent of the Naval 

 Observatory. 



i On the Mode of Observing the Coming Transits of Venus, A mer. Jour. Sri. and Arts, SO, 74-83, 1870. 



