The task of writing an account of the cathedral of Notre Dame is materially lightened by the minute details of its history and architecture to be found in the various writings of M. Viollet-le-Duc, of which, unfortunately, the Library of the British Museum does not contain a complete set. The Description de Notre Dame, published in 1856 by M. de Guilhermy in conjunction with M. Viollet-le-Duc, contains much useful material, while the splendidly illustrated account of the church in the first volume of Paris a travers les Ages is full of interesting archæological particulars. As the numerous other authorities which have been used are quoted in the text, it is unnecessary to enumerate them here. The writer has found Mr. Charles Herbert Moore's Development of Gothic Architecture useful in not a few difficult matters. He wishes specially to thank Mr. Edward Bell for valuable suggestions on many important points.