The principal literary sources for the work are listed in the bibliography, though many works not mentioned were also consulted. Among the sources which proved most useful are the works of Choisy, Enlart, Lasteyrie, Rivoira, Porter and Moore, all of which are especially recommended to the student of vaulting. For personal assistance in the preparation and subsequent reading of the work, the author is much indebted to Professor Howard Crosby Butler and Professor Frank Jewett Mather, Jr., of Princeton University, but especially to Professor Allan Marquand of Princeton, under whose inspiration and encouragement the work was undertaken. CLARENCE WARD. New Brunswick, New Jersey. October, 1915. CONTENTS CHAPTER I. NAVE AND AISLE VAULTS 1 CHAPTER II. TRANSEPT AND CROSSING VAULTS 105 CHAPTER III. APSE VAULTS 124 CHAPTER IV. AMBULATORY VAULTS 158 CHAPTER I NAVE AND AISLE VAULTS During the Romanesque period, or roughly speaking, from the beginning of the eleventh to the middle of the twelfth century, three chief forms of vaulting were employed over the naves and aisles of church edifices. The first of these was the dome, the second the tunnel vault, and the third, groined vaulting. With the development of the ribbed vault, all three gave way to this new method of construction, and the Gothic era was inaugurated. DOMES ON SPHERICAL PENDENTIVES The dome was employed in two rather distinct ways according to the form of pendentives used for its support. Thus a number of churches continue the tradition of the spherical pendentive, while in others some form of squinch or trumpet arch is found. Both methods are of early origin, dating back, in fact, to the Roman era preceding the reign of Justinian (483-565) and consequently earlier than the Byzantine architecture of which they are so conspicuous a feature. Rivoira[1] has shown the existence of numerous spherical pendentives of the second century A.D. or even earlier, and Lasteyrie[2] has added to these a small cupola at Beurey-Beauguay (Côte-d’Or) in France dating from the second or third century. But even if this method were known at an early date it was not until the Byzantine era that it obtained a wide-spread and extensive usage. During the sixth century it became the principal method of vaulting throughout the Roman Empire, and, as such, had a considerable influence upon Carolingian architecture of the ninth and tenth centuries. This is true even in France, for traces of pendentives were found in 1870 during a restoration of the church of Germigny-des-Prés,[3] a fact of particular interest because it is in France that the principal Romanesque examples of this method are to be seen. DOMES ON SQUINCHES