To unfold that interesting and dramatic period which opened with the return of Pius IX. and closed with the fall of the temporal power, it was necessary to pause and weigh the mass of publications issued concerning the epoch, besides searching among private archives and familiar correspondence and also questioning survivors. More than once I was discouraged, and felt tempted to abandon the enterprise. Only the passion for research supported me in this arduous labour, which often appeared indiscreet and was often painful, because it destroyed many a legend, dashed many a prejudice, and...