ROOD, OGDEN NICHOLAS

(b. Danbury, Connecticut, 3 February 1831; d. New York, N.Y., 12 November 1902)

physics.

The son of Anson Rood, a Congregational minister, and Alida Gouverneur Ogden, Rood graduated from the College of New Jersey (Princeton) in 1852 and did postgraduate work from 1852 to 1858 at Yale, Munich, and Berlin. Married in 1858 to Matilde Prunner of Munich, he then joined the staff of the University of Troy, a newly founded but short-lived denominational institution in Troy, New York, as professor of chemistry. In 1863 Rood was appointed professor of physics at Columbia University, where he served until his death, and in 1865 he was elected to the National Academy of Sciences.

A talented and prolific experimentalist, Rood managed to measure the duration of a spark discharge in a Leyden jar and the high resistance of dielectrics. He also found a way to produce and measure the magnitude of vacuums in the range of 10⁻⁹ atmospheres. Perhaps his most significant contribution to science was his technique of flicker photometry for comparing the brightness of different colors. The photometry of brightness depends upon the direct visual comparison of two adjacent fields of illumination, and the eye cannot make the judgment if the two fields are unequal in wavelength. Rood pointed out that since one saw a flicker when two differently colored surfaces were alternatively illuminated by lights of unequal brightness, the intensities were the same when the flicker disappeared.

An accomplished painter, Rood had a specially keen interest in physiological optics and theories of color. In addition to his research in this area, in 1879 he published Modern Chromatics, a popular summary of the field addressed to both physicists and artists. The book was widely read by painters in both Europe and the United States and was known as “the impressionist’s Bible.” Ironically, Rood himself disliked the impressionists and once said, “If that is all I have done for art, I wish I had never written that book.”

BIBLIOGRAPHY

Edward L. Nichols, “Ogden Nicholas Rood,” in Biographical Memoirs. National Academy of Sciences, 6 (1909), 447–472, is a useful résumé and contains a complete bibliography of Rood’s writings. About 1,000 items, including papers, correspondence, sketchbooks, drawings, etchings, photos, and memorabilia, are in the Columbia University Library.

Daniel J. Kevles