Historians, palæographers, and archaeologists, will all agree that it is very important to determine the places in which ancient books were written or preserved. If we can trace the career of a manuscript from the scriptorium where it took shape to the library shelf on which it rests to-day, we may find that its history will throw light on the most unexpected matters. It may shew us the origin of a school of handwriting: it may explain the genesis of a type of text: or it may account for the presence of a particular element in the works of a famous writer. Some of the notable results gained by study of the history of individual manuscripts will appear as I proceed. They are probably sufficient to justify the rash attempt I have made to determine the original homes of the books comprising that famous collection, the Parker MSS. at Corpus Christi College. I say that my attempt is rash, because it is not to be expected that any one person should be capable of seizing upon and rightly appreciating all the indications which are significant and might be made to yield the information we seek. Still, it so happens that a very considerable proportion of the books in Archbishop Parker's collection can be assigned to their ancient homes with certainty, or with great probability; and, for the rest, I have noted such indications as may in the future enable myself, or other searchers in the same field, to fill up the gaps I have been forced to leave.