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SCIENCE. 



[N. S. Vol. XVII. No. 433 



Venus Commission to pursue the same 

 course. To combat that idea, Professor 

 Hai-kness published an elaborate paper ' On 

 the Relative Accuracy of Different Methods 

 of Determining the Solar Parallax,' which 

 was immediately translated and reprinted 

 in Prance, with the result that both the 

 United States and Prance decided to con- 

 tinue the use of photography. In 1882, as 

 the principal executive officer of the United 

 States Transit of Venus Commission, Pro- 

 fessor Harkness fitted out all the United 

 States Government parties for observing 

 the transit which occurred on December 

 6, of that year, and observed it himself 

 at a station established on the grounds of 

 the Naval Observatory, Washington, D. C. 

 The work of reducing all the observations 

 obtained by the variovis parties was as- 

 signed to him, and with the aid of a small 

 corps of assistants he completed it in a 

 little more than six years, the final result 

 for the value of the solar parallax from 

 the photographs being obtained on Peb- 

 ruary 13, 1889. During the years 1889 

 and 1890 he devoted miich time to the prep- 

 aration of his work on ' The Solar Parallax 

 and Its Related Constants, ' which was pub- 

 lished in 1891, -and from that date until 

 December, 1899, he was principally oc- 

 cupied with matters relating to the build- 

 ing of the new Naval Observatory, in de- 

 vising and mounting its instruments and 

 apparatus, and in establishing a proper 

 system of routine observing. In 1891 he 

 drew up the specifications for the construc- 

 tion of the 12-inch equatorial telescope, and 

 for the repairing and remounting of the 

 26-inch equatorial telescope, the 8.5-ineh 

 transit circle, the meridian transit instru- 

 ment and the prime vertical transit instru- 

 ment. In 1894 he prepared detailed specifi- 

 cations for the construction of the 6-inch 

 steel transit circle, and in 1895-96 he ar- 

 ranged all the details for the construction 



of the 5-inch steel alt-azimuth instrument. 

 All these instruments are now mounted in 

 the new Naval Observatory, and their prin- 

 cipal parts are proportioned in accordance 

 with general formulte which Professor 

 Harkness deduced from an examination of 

 the drawings and specifications of nearly 

 all the large instruments which have hither- 

 to been constructed for the great observa- 

 tories of the world. Among the novelties 

 introduced in these instruments by Pro- 

 fessor Harkness may be mentioned the dials 

 which face the observer when using the 

 quick motions of the equatox-ial telescopes, 

 and constantly indicate the exact right 

 ascension and declination of the points in 

 the heavens to which these telescopes are 

 directed, and the construction of the 6-inch 

 transit circle and the 5-inch alt-azimuth 

 instrument entirely of steel, including the 

 telescope tubes and their axes, which are 

 machined both inside and out, so as to re- 

 duce flexure to a minimum. On October 

 21, 1892, Professor Harkness was appointed 

 chief astronomical assistant to the Superin- 

 tendent of the Naval Observatory, and on 

 September 21, 1894, he was appointed 

 Astronomical Director of the Naval Ob- 

 servatory, with complete control of all its 

 astronomical work. In addition to the 

 astronomical directorship, he was appointed 

 Director of the Nautical Almanac on June 

 30, 1897,. and both of these offices he held un- 

 til his detachment from all duty on Decem- 

 ber 15, 1899, preliminary to his retirement 

 for age on December 17, 1899, when he 

 was promoted to the rank of rear-admiral. 

 Professor Harkness has published many 

 scientific papers, and is a member of 

 numerous scientific societies. He was 

 president of the Washington Philosophical 

 Society in 1887, vice-president of the 

 American Association for the Advance- 

 ment of Science in 1881 and 1885, and its 

 president in 1893. 



