The Historical Library of Diodorus the Sicilian/Book XIII/Preface

Preface
IF we should imitate others in the compiling of their histories, we should first in the preface of every book, observe some things pertinent to the occasion and subject in hand, and then descend to the continuation of our discourse, upon the actions and affairs that follow next in order: for by some small intermission from writing, we gain a breathing fit; the fruit and advantage by prefaces. But inasmuch as we have promised to endeavour in a few books, not only to relate things that have been done, but likewise to comprehend in that relation, the time of above eleven hundred years, it is necessary to avoid prefaces, and come presently to the matters in hand. Only premising this to inform the reader, that in the six former books are contained the things done in all parts of the world, from the Trojan war to the time the Athenians decreed the war against the Syracusans, to which, from the destruction of Troy, is seven hundred and threescore years: and that we shall begin this book with that expedition against the Syracusans, and end it at the beginning of the secoud Carthaginian war against Dionysius the tyrant of Syracuse.