I have been exceedingly fortunate in the architects who have given me the benefit of their professional knowledge and skill in the execution of my task, and I beg that their share in this work should be recognized and appreciated as fully as it deserves. To the generosity of the British School at Athens I am indebted for being able to secure the services of Mr. Ramsay Traquair, Associate of the Royal Institute of British Architects and Lecturer on Architecture at the College of Art in Edinburgh. Mr. Traquair spent three months in Constantinople for the express purpose of collecting the materials for the plans, illustrations, and notes he has contributed to this work. The chapter on Byzantine Architecture is entirely from his pen. He has also described the architectural features of most of the churches; but I have occasionally introduced information from other sources, or given my own personal observations. I am likewise under deep obligation to Mr. A. E. Henderson, F.S.A., for the generous kindness with which he has allowed me to reproduce his masterly plans of the churches of SS. Sergius and Bacchus, S. Mary Panachrantos, and many of his photographs and drawings of other churches in the city. I am, moreover, indebted to the Byzantine Research and Publication Fund for courteous permission to present here some of the results of the splendid work done by Mr. W. S. George, F.S.A., under unique circumstances, in the study of the church of S. Irene, and I thank Mr. George personally for the cordial readiness with which he consented to allow me even to anticipate his own monograph on that very interesting fabric. It is impossible to thank Professor Baldwin Brown, of the University of Edinburgh, enough, for his unfailing kindness whenever I consulted him in connection with my work. Nor do I forget how much I owe to J. Meade Falkner, Esq., for kindly undertaking the irksome task of revising the proofs of the book while going through the press. I cannot close without calling attention to the brighter day which has dawned on the students of the antiquities of Constantinople since constitutional government has been introduced in the Ottoman Empire. Permission to carry on excavations in the city has been promised me. The archaeology of New Rome only waits for wealthy patrons to enable it to reach a position similar to that occupied by archaeological research in other centres of ancient and mediaeval civilizations. But the monuments of the olden time are perishable. Of the churches described by Paspates in his _Byzantine Studies_, published in 1877, nine have either entirely disappeared or lost more of their original features. It was no part of wisdom to let the books of the cunning Sibyl become rarer and knowledge poorer by neglecting to secure all that was obtainable when she made her first or even her second offer. ALEXANDER VAN MILLINGEN. ROBERT COLLEGE, CONSTANTINOPLE. [Greek: Polis ekklêsiôn galouche, pisteôs archêge, orthodoxias podêge.]