(b. Axstedt. Germany, December 1757; d. Hamburg, Germany, 20 April 1837)
The son of a farmer, Woltman, while quite young, taught school, presumably at Axstedt. Within a short time, however, he was transferred to the part of the Ritzebüttel district that borders on the North Sea between the Elbe and Weser rivers, an area where the shore-erosion problem constitutes a challenge to the best hydraulic engineers. During the previous century its protection facilities had been destroyed by storms and floods at least seven times. Developing stronger means of protection became an early and primary objective of Woltman’s career.
In May 1779, Woltman was appointed an under-inspector and clerical employee in the office responsible for erecting and maintaining the erosion-control structures. The following year he began taking courses in mathematics and architecture at Hamburg, and later at the universities of Kiel and Göttingen, Woltman subsequently made a journey during which he met skilled workers in hydraulics at Frankfurt, Strasbourg, Paris, Cherbourg, Calais, Dover, London, and Holland. Upon his return to Ritzebüttel on 20 November 1784, he began work on the local erosion problem.
Woltman’s first book, Theorie und Gebrauch des hydrometrischen Flügels (1790), drew attention to the extensive use in England and Holland of wind and water power. That, he contended, should be done in the Hamburg area, and added that if his idea was adopted, frequent measurements of wind and water velocities could provide data of great value. The remainder of his book was devoted largely to the instruments he had designed for that purpose.
The four-volume Beiträge zur hydraulischen Architektur (1791–1799) immediately attracted attention in the scientific community with the first volume, which concerned the management of dikes and reinforcing shorelines. In 1792 Woltman became a member of the Hollandsche Maatschappij der Wetenschappen, at Haarlem; and the Bataafsch Genootschap der Proefondervindelijke Wijsbegeerle, at Rotterdam: and was offered membership in the Königliche Gesellschaft der Wissenschaften, at Prague. In the following year he received an offer to join the Königliche Akademie der Wissenschaften, at Göttingen.
On 1 October 1797 Woltman married Johanna Schuback, the daughter of his first patron. They had five children.
Antoine Chézy (1718–1798) and Pierre Du Buat, contemporaries of Woltman’s, conceived what may have been the earliest valid equations concerning the velocity of flowing water. Woltman probably never heard of Chézy, whose formula attracted little attention until 1897, when Clemens Herschel wrote an article about it. Du Buat’s work (published in 1779 under the title Principes d’hydraulique), however, received immediate and highly favorable attention. Its velocity equation was so complicated and so difficult to apply that Woltman recommended a much simpler one. Much of its simplification was made possible by experiments that Woltman had conducted and that justified the use of powers (exponents) for velocity ranging from 1.75 (for pipes) to 2 (for open channels). Those values, as noted by Hunter Rouse, “are precisely the limits now accepted,”
The invention of Woltman’s water current meter in 1790 brought him the most lasting fame. One of the original models has been preserved at the Deutsches Museum in Munich, and a replica of it is on display at the National Museum of History and Technology in Washington, D.C.
Just before he constructed the current meter, Woltman had designed two anemometers, one of which was intended to be mounted on a standard and the other to be held in one’s hand. These, he admitted, were largely patterned after C. G. Schober’s anemometer (described in the 1752 editions of the Hamburgisches Magazin). After numerous futile attempts to evaluate, both experimentally and mathematically, the relationship be-tween the speed of their rotors and the velocity of the sind, he decided to calibrate them in still water. That procedure was successful, and it convinced him that with only a minor change (reducing the rotor to about one-third of its original size), the device would be suitable for measuring the velocity of water flowing in rivers. He there upon ordered his mechanic (a man named Steinmetz, in Chxhaven) to build such a model. The ancestry bof practically all of the propeller-type current meters in use today can be traced to that particular model.
For many years after Woltman announced that meter’s invention, most of the improved versions of it were called “Woltman meters” as a courtesy to him (a commendable practice, but one that unfortunately has resulted in his having erroneously been credited in many modern textbooks and magazines with having build a better instrument than he actually designed). A somewhat similar practice is presently being carried on with respect to the type of meters that measure the amount of water flowing through pipes supplying homes and office buildings. In some instances modern engineers have applied the Woltman principle of operation to such meters, and have identified them as “Woltman meters.”
I. Original Works. Woltman’s first published work was Theorie und Gebrauch des hydrometrischen Flügels oder eine zuverlässige Methode die Geschwindigkeit der Winde und strömenden Gewässer zu beobachten (Hamburg, 1790). His other major work was Beiträage zur hydraulischen Architektur, 4 vols (Göttingen, 1791–1799).
II. Secondary Literature. Allegemeine deutsche Biographie, XLIV, 192–199, lists the titles of several additional works by Woltman relating to canals, navigation, and shore protection. Also see Hegell, “Die Urform des Woltmanschen Flügels,” in Zeitschrift des Verbands deutscher Architekten- und Ingenieurvereine (11 Apr. 1914), 129–130; Steponas Kolupaila, Bibliography of Hydrometry (Notre Dame, Ind., 1961). 12, 282, 326. 328–329; and Hunter Rouse and Simon Ince, History of Hydraulics (Ann Arbor, Mich., 1957), 134–136. 141.
Arthur H. Frazier