WILLIS, ROBERT

(b. London, England, 27 February 1800; d. Cambridge, England, 28 February 1875)

engineering, medieval archaeology.

The son and grandson of distinguished physicians, Willis was educated privately until he entered Gonville and Caius College, Cambridge, where he obtained the B.A. and was elected fellow in 1826. The next year he was ordained deacon and priest. In 1837 he succeeded William Farish as Jacksonian professor of natural and experimental philosophy at Cambridge, a position he held until his death. His major contributions were to the kinematics of mechanisms and the study of the architecture of the Middle Ages.

As Jacksonian professor, Willis delivered lectures on “mechanical philosophy” and applied his considerable inventive skills to the improvement of a set of machine parts for the construction of demonstration models. By modifying Farish’s original concepts, Willis reportedly was able to popularize what may well have been the first mechanical model-building kit. His lectures formed the basis for his book, Principles of Mechanism (1841).

Willis was one of the first clearly to enunciate the importance of excluding causal forces in the study of the motion of machinery. He introduced the term “kinematics,” as an anglicized version of the French cinématique, thereby originating the English name of the branch of mechanics that deals with the geometry of motion without regard to the forces causing it. He felt it was important to change the study of machinery from a descriptive to an analytic science. Although his analytical treatments were modest by modern standards, Willis’ advocacy of a systematic approach to the design of machine mechanisms anticipated and encouraged the subsequent development of kinematic analysis and synthesis of mechanisms. He organized mechanisms according to an original classification scheme, little of which is in use today although it was quite popular until almost 1900.

By 1870, when an enlarged second edition of his book was published. Willis was able to point out that all (thirteen) books on mechanisms published (in England and France) in the previous twenty-two years utilized his classifications and nomenclature. The present ideas on classification, however, are derived mainly from Franz Reuleaux, who published his landmark book in the year of Willis’ death. Of lasting value was Willis’ chapter on gear teeth. Taken from an earlier paper (1838). In this outstanding work he introduced the idea of manufacturing sets of interchangeable gears, pointed out the convenience of 14.5° involute gear teeth (in common use today), and described his invention of a device to facilitate the approximate layout of gear teeth. (He coined the name “odontograph,” which has become the generic term for devices used to assist in that process.) His book remains the earliest attempt to develop a complete treatment of the science of machine kinematics.

Willis studied architecture and archaeology with great enthusiasm and expertise, becoming an authority on medieval Latin and construction techniques. In 1835 he published an essay that is reputed to have been the first work to call serious attention to the Gothic style of architecture. He then invented a device (the “cymograph”) for copying architectural moldings. Subsequently he published studies detailing the original construction and the later modifications to the cathedrals of Hereford, Canterbury, Winchester, York, Chichester, and Worcester and the abbey churches of Glastonbury and Sherborne. To all these works he brought such great skills in antiquarian research and keen insight that most of these works are still regarded as the definitive studies of these churches. He continued his archaeological writings until his health became seriously impaired, several years before his death.

Willis’ earliest works include an analysis of a well-known mechanical chess player, which he correctly proved was a hoax (1821), and three papers applying mathematical analysis to the flow of air. The last of these (1828- 1829) describes the action of the larynx. As a result of this work he was elected to the Royal Society (1830). Willis served on government commissions in such diverse fields as structures and astronomy, and participated in two international expositions. He held honorary membership in and medals from various learned societies, and in 1862 was president of the British Association for the Advancement of Science.

BIBLIOGRAPHY

I. Original Works. A complete list of works published during Willis’ lifetime is given in his book, Principles of Mechanism, 2nd ed., enl. (London, 1870), the title page of which contains a list of his honors and more prominent affiliations. Eleven years after Willis’ death his nephew and biographer, John Willis Clark, completed and published Willis’ The Architectural History of the University and Colleges of Cambridge, 4 vols. (Cambridge, 1886), written with T. W. Clark.

II. Secondary Literature. Dictionary of National Biography. XXI, 492–494, contains an excellent biography by John Willis Clark. Abbreviated biographical data are in J. A. Venn, Alumni Cantabrigienses, pt. II, VI (Cambridge, 1954). Venn includes some items that Clark omits, and differs with Clark on several minor dates. For a historical perspective on Willis’ mechanism work see R. S. Hartenberg and J. Denavit, Kinematics of Linkages (New York, 1964). 16. 70–75 : and E. S. Ferguson, “Kinematics of Mechanisms From the Time of Watt,” Contributions. Museum of History and Technology, United States National Museum, paper 27 (Washington, D.C., 1962). For historical perspective on Willis’ architectural studies one apparently must consult books on the various cathedrals. See, for example, the intro. to H. R. Williamson, Canterbury Cathedral (London, 1953).

Bernard Roth