Before proceeding further with the architectural history of the cathedral (as distinguished from the description of it, which will be given in due course), it may be well to say a few words upon the principles which have guided the writer in his treatment of the subject. These cannot be better expressed than in a very pithy sentence uttered by Professor Willis at the meeting of the Archaeological Institute at this very place in 1861. "In all investigations of this nature, I am of opinion that it is requisite to ascertain first whether there exist any contemporary documents which may throw light upon the history of the fabric, and then to let the stones tell their own tale." Now there is an abundance of documentary evidence for our purpose; but recent criticism has shewn that not all is to be relied upon as authentic. And the Latin expressions for different portions of the building can, in many instances, not be interpreted with certainty; while the absence of all reference to some works of importance (the West Front, for example), is very mysterious. Most of these documents had been studied in manuscript by Gunton and Patrick, and the result of their studies was published in 1686. The work is entitled "The History of the church of Peterburgh ... By Symon Gunton, late Prebendary of that church.... And set forth by Symon Patrick, D.D., now Dean of the same." Gunton was Prebendary from 1646 to his death in 1676; Patrick was Dean from 1679 till his consecration as Bishop of Chichester in 1689. Most of the documents in question have since been printed. Two writers in the last half century have published monographs on the cathedral, both of great value, both treating the subject after Professor Willis's method. These are G.A. Poole, formerly Vicar of Welford, whose paper on the Abbey Church of Peterborough was published among the Transactions of the Architectural Society of the Archdeaconry of Northampton in 1855, and the late Professor F.A. Paley, a second edition of whose pamphlet, "Remarks on the Architecture of Peterborough Cathedral," was issued in 1859. It by no means detracts from the value of the method employed that the results of the investigations of these two careful students of the fabric do not accord with one another. Much must always be left to inference or conjecture. Since they wrote many discoveries have been made which have shewn some of their conclusions to have been inaccurate. But the rule is a sound one, and indeed it is only by studying the documents and the fabric together that one can hope to learn the history of any great building.