William Harkness was born in Ecclefechan, Scotland on December 17, 1837. He came to the United States in 1839. He studied at Lafayette College from 1854 to 1856, and at the University of Rochester from 1856 to 1858, from which he graduated. He then studied medicine at the New York Homeopathic Medical College, and served as a volunteer surgeon during the Civil War. On August 1, 1862 he was appointed as aide to the United States Observatory, and professor of mathematics there in 1863. From 1865 to 1866 he served aboard the U.S.S. Monadnock. On the cruise from Philadelphia to San Francisco he investigated the variations of the compass. His report was published in 1871 by the Smithsonian Institution. He was then attached to the United States Hydrographic Office. During a total eclipse of the sun in 1869 he discovered the coronal line K 1474. In 1871 he was appointed as one of the members of the Transit of Venus commission. He was in charge of the transit of Venus parties in 1874 at the theory of the focal curve of achromatic telescopes in 1879. His inventions of better photographic equipment and methods made possible new accuracy in the measurement of distances to Venus, and to the sun and their relative positions. He retired from the Navy with the rank of rear admiral. He died in 1903 at Jersey City, New Jersey.