Light, Wind, and Structure: The Mystery of the Master Builders by Robert Mark

Abstract

408 Book Reviews TECHNOLOGY AND CULTURE Light, Wind, and Structure: The Mystery of the Master Builders. By Robert Mark. Cambridge, Mass.: MIT Press, 1990. Pp. xvii + 209; illustra­ tions, glossary, notes, index. $19.95. This handsomely illustrated, beautifully produced book is one of a series of monographs supported by the Alfred P. Sloan Foundation as part of its New Liberal Arts Program, the goal of which is “to involve (liberal arts) undergraduates in meaningful experiences with technol­ ogy ... in a wide range of subjects and fields.” Robert Mark combines modern techniques—dimensional analysis, computer simulation, and photoelastic modeling—with a close reading of the historical record to evaluate the structural soundness and the efficiency of great classic edifices of the past: the Pantheon, Hagia Sophia, several Gothic cathedrals of northeastern France, and St. Paul’s Cathedral. He speculates on the design and construction procedures of their (some­ times unknown) builders. Given the materials, the largely empirical knowledge, and the societal context of the time, he then infers some enduring lessons about the nature of the structural art and the relation of function to form and shows how they apply to spectacular structures of the 19th and 20th centuries. The ancient buildings studied here were designed for large con­ gregations to take part in religious services. Their buttressed walls and their domed or vaulted ceilings had to enclose substantial unobstructed covered space and admit natural sunlight filtered and focused to enhance the solemnity of the rites conducted within. Their size and splendor symbolized the faith, the wealth, and the power of the communities and rulers who decided, financed, and organized their construction. At the same time, their structures had to withstand the loads imposed by gravity, by the uneven settling of their founda­ tions, and by the winds to which their height exposed them. How did their master builders achieve the size, the elegance of form, and the mystical play of light that still astonish us? Their materials were pozzolana (Román cement), stone, and brick and mortar. They knew from long experience that these materials would support large loads in compression but fail in shear or tension. Therefore, as the unobstructed area to be covered increased, the roofing could not be a set of horizontal beams or slabs supported by columns (as it is in a Greek temple) because a beam bends under its own weight so that its upper half is in compression and its lower half is in tension. The alternative developed by Roman builders was a dome or cylindrical vault that is wholly in compression but exerts an outward lateral load on the walls that support it—hence the need to buttress the wall laterally from the outside to balance that load. This is the basic construction formula that underlies all monumental cement, stone, and brick construction, which prevails until the use of TECHNOLOGY AND CULTURE Book Reviews 409 iron or steel, either as a structural construction material or as a component of reinforced and prestressed concrete. The buildings examined by Mark represent variations on that basic theme. Mark brings together a set of examples to demonstrate the diversity and the opportunity for growth, both in size and in complexity, which are inherent in the basic dome and vaulted arch schemes. That development—from the Pantheon through Hagia Sophia, the Cathe­ dral in Florence, and St. Peter’s in Rome to Christopher Wren’s St. Paul’s, and from Paris through Chartres and Bourges to Reims and Amiens—seems supported by experience gained from the observa­ tion and study of standing buildings, and from careful attention to any cracks that might develop during the slow process ofbuilding. The experience was quite sophisticated. For example, the lessons from major accidents or miscalculations (e.g., the collapse of the original dome of Hagia Sophia as a consequence of an earthquake or of the choir vaults at Beauvais probably due to wind loads on improperly butting buttresses) were incorporated in subsequent designs. Mark attributes the success of the great master builders to their reliance on experience strengthened by close contact between design and construction and to the economic pressure to reduce structural weight. The resulting technical solutions (e.g., arched...