Robert Willis, Viollet-le-Duc and the structural approach to Gothic architecture / Robert Mark -- On the rubber vaults of the Middle Ages and other matters / J. Heyman -- The geometrical knowledge of mediaeval master masons / Lon R. Shelby -- Villard de Honnecourt, Reims, and the origin of Gothic architectural drawing / Robert Branner -- The tracing floor of York Minster / J.H. Harvey -- Late Gothic structural design in 'instructions' of Lorenz Lechler / Lon R. Shelby and R. Mark -- The ground plan of Norwich Cathedral and the square root of two / Eric Fernie -- The stonework planning of the first Durham master / Jean Bony -- Archaeology and engineering: the foundations of Amiens Cathedral / S. Bonde, C. Maines and R. Mark -- The collapse of 1284 at Beauvais Cathedral / S. Murray -- Beauvais Cathedral / J. Heyman -- The structural behaviour of medieval ribbed vaulting / K.D. Alexander, R. Mark and J.F. Abel -- Fan vaulting / Walter C. Leedy, Jr. -- 'Ars mechanica': Gothic structure in Italy / Elizabeth Bradford Smith -- Brunelleschi's dome of S. Maria del Fiore and some related structures / Rowland J. Mainstone -- A comment on the function of the upper flying buttress in French Gothic architecture / John F. Fitchen -- The high roofs of the east end of Lincoln Cathedral / N.D.J. Foot, C.D. Litton and W.G. Simpson -- Viollet-le-Duc and the fleche of Notre-Dame de Paris: Gothic carpentry of the 13th and 19th centuries / Lynn T. Courtenay -- Building the tower and spire of Salisbury Cathedral / Tim Tatton-Brown