With the author's manuscript and printed copy before me, my own work as editor has consisted chie?y in selecting the material and seeing it through the press. Some omitted references have been sup plied; a few slips of the pen or the press, formerly overlooked, have been corrected; unwieldy paragraphs have been broken up, and the punctuation has been simplified; but nothing new has been added to text or notes. I am responsible for the choice of a title.