'Now, although it had seemed fit that the aforesaid work should be divided into three short books to relieve the mind; for in some way or other, as the blessed Augustine says: “The attention of the reader is refreshed by the termination of a book, as the toil of the traveller by resting at an inn" [Contr. adv. leg. et. proph., Bk. I. Ch. 33]; nevertheless, that it might be rendered more easy for those who search to find, it was thought good that the continuous order of paragraphs should be preserved through out, which I had previously noted in the book itself by prefixing marks.' From the letter to Eusebius.