382 WILLIAM HARKNESS 



observatory on several occasions to observe eclipses, and was 

 absent for about a year in charge of an expedition to Tasmania 

 to observe the transit of Venus of 1874. 



His long career in the government service was characterized 

 by the most conscientious and indefatigable industry. Into the 

 large projects which were committed to his care, especially those 

 of fitting out the American parties for observing the transits of 

 Venus of 1874 and 1882, and the building and equipping of the 

 new Naval Observatory, he entered with a zeal and a fidelity 

 which taxed often to the verge of exhaustion his strong frame 

 and his vigorous mind. He had a highly developed capacity 

 for mechanical invention, and he devised many instruments and 

 pieces of apparatus noteworthy for their ingenuity and effec- 

 tiveness. He was an unusually skillful experimentalist, and 

 was thus able to remedy with his own hands many defects of the 

 instruments he employed. His wide experience as an observer 

 of astronomical and other physical phenomena, and his intimate 

 knowledge of ways and means available for securing measure- 

 ments of precision, made him one of the first authorities of his 

 time in these subjects. 



Although his life was especially busy with what may be 

 called the engineering side of astronomy, he found time to pre- 

 pare many papers, reports and semi-popular scientific addresses. 

 Of these products of his fertile and suggestive mind, it may 

 suffice here to mention the memoir to which he justly attached 

 most importance, namely, that on "The Solar Parallax and Its 

 Related Constants," published in 1891. In this paper he takes 

 the independently observed values of the many constants of the 

 solar system and adjusts them by the method of least squares to 

 conformity with the necessary conditions which exist among 

 them. This was an original and a bold contribution, the merits 

 of which are, perhaps, not yet generally appreciated, but it 

 must surely take rank along with the important advances in 

 astronomy of the nineteenth century. 



Professor Harkness was twice vice-president of the section of 

 astronomy and mathematics of The American Association for 

 the Advancement of Science, in 1881 and 1885, and president 

 of the same Association in 1893. He was president of the 



