Bowie, William

(b. Grassland, Anne Arundel County, Maryland, 6 May 1872; d. Washington, D.C., 28 August 1940)

geology.

Bowie was descended from two old Maryland families. He began his advanced education at St. Johns College, Maryland, and completed his B.S. degree at Trinity College in Connecticut, where in 1907 he earned the M.A. In 1895 his early career preparation was completed when he received a C.E. degree from Lehigh University.

Bowie’s lifelong association with the U.S. Coast and Geodetic Survey began in Washington in July 1895. As a junior officer he began fieldwork, acting as party chief for triangulation and base measurement teams in many states, Alaska, Puerto Rico, and the Philippines. In 1909 he was made chief of the Survey’s Division of Geodesy.

Bowie completed many projects of national significance in his more than forty years with the Survey. As chief of the Division of Geodesy he established many needed controls over triangulation and leveling surveys, as well as over studies for determining gravity effects at different locations in the United States.

To eliminate inaccuracies in triangulation, Bowie sponsored the improvement of theodolites, including the substitution of silver circles for bronze. In a series of papers and articles, he became an articulate propagandist for the production of more accurate maps, impressing upon both his colleagues and the public the extent of this need.

Bowie also achieved acceptance and use of the North American Datum by the United States, Canada, and Mexico. This geodetic datum consists of the latitude and longitude of one station and the azimuth from this station to another station. The three governments agreed upon the Meades Ranch Triangulation Station in Kansas as the initial point for setting up triangulation surveys.

To avoid costly duplication of map services within the government, Bowie pressed for the establishment of the Federal Board of Surveys and Maps in 1919 and for the creation of a Division of Surveys and Mapping in the American Society of Civil Engineers.

Much of Bowie’s importance as a scientist lies in his presentation of theories of isostasy. His research in this area dates from 1912. His early studies had been of the relations between gravity anomalies and geologic formations, and his findings on these unbalanced areas were presented accurately. His investigations in isostasy were the subjects of numerous official Survey publications, culminating in the publication of his book Isostasy (1927).

In isostatic investigations, Bowie carried on the work of two British observers, Airy and Pratt, and extended the research of two Americans, Dutton and Hayford, the latter a senior colleague in the Survey. In 1855 Pratt had explained the cause of abnormal plumb-line deflections near mountain ranges by theorizing that such an earth mass was compensated for by a deficiency in the mass of rock below it; that it would be less dense than the mass underlying the plain adjacent to the range. For this balancing phenomenon Dutton later used the term isostasy, meaning “equal standing,” for the condition was one of equilibrium between the earth’s outer material and that below. What was termed the “level of isostatic compensation” was located at the depth at which a balance existed.

Bowie also refined the hypothesis of Pratt and Hayford that mountains had been uplifted from the underlayer like “fermenting dough.” He stated that over long periods, erosion and sedimentation had caused the earth’s crust to become overloaded. There had followed a compensating action within the crust, light rock being pushed upward. Subcrustal matter then entered the crustal spaces to restore balance.

Again following the lead of Hayford, Bowie also computed reduction tables for the depths of compensation, using data from gravity values and information from deflection readings in many locations. As a result of this detailed study, Bowie was recognized as bringing the study of isostasy into the realm of mathematical computation. The methods of his research on this problem paralleled his efforts within the Survey to secure purely scientific data beyond the agency’s function of producing information for practical use alone.

Bowie also supported the idea that the crust of the earth under oceans was in isostatic equilibrium. Familiar with the work of F. A. Vening Meinesz, who had developed a method of accurately determining gravity over ocean areas, and eager to improve measurement methods, he arranged for the U.S. government and interested agencies to work with the Dutch scientist and authorities in 1928 and in 1931–1932 on expeditions recording gravity values at sea. A significant conclusion of the study, which Bowie included in his book Isostasy, was that isostatic compensating levels began at the physical earth’s surface, and not at sea level.

Before his death Bowie’s reputation was international. He was a member of over thirty professional organizations, including the National Academy of Sciences, the American Geographical Society, and the Geological Society of America. He was particularly active in two related organizations that he served as president: the International Association of Geodesy and its larger affiliate, the International Union of Geodesy and Geophysics.

A list of nearly 400 articles and papers written by Bowie during his active career (compiled as part of a memoir by the National Academy of Sciences) attests, in a measure, to the nature and the range of his accomplishments.

BIBLIOGRAPHY

Bowie’s major work is Isostasy (New York, 1927). A bibliography of his articles and papers is in J. A. Fleming, Biographical Memoir, pp. 79–97.

Works on Bowie are J. A. Fleming, Biographical Memoir of William Bowie, 1872–1940 (Washington, D.C., 1949); N. H. Heck, “Memorial to William Bowie,” in Proceedings of the Geological Society of America, 40 (June 1941), 163–166; and W. Heiskanen, “William Bowie as an Isostasist and as a Man,” in Transactions of the American Geophysical Union, 30 (Oct. 1949), 629–635.

Cortland P. Auser