The history of Philip the Second is the history of Europe during the latter half of the sixteenth century. It covers the period when the doctrines of the Reformation were agitating the minds of men in so fearful a manner as to shake the very foundations of the Romish hierarchy in the fierce contest which divided Christendom. Philip, both from his personal character, and from his position as sovereign of the most potent monarchy in Europe, was placed at the head of the party which strove to uphold the fortunes of the ancient Church; and thus his policy led him perpetually to interfere in the internal affairs of the other European states,--making it necessary to look for the materials for his history quite as much without the Peninsula as within it. In this respect the reign of Ferdinand and Isabella presents a strong contrast to that of Philip the Second; and it was the consideration of this, when I had completed my history of the former, and proposed at some future day to enter upon that of the latter, that led me to set about a collection of authentic materials from the public archives in the great European capitals. It was a work of difficulty; and, although I had made some progress in it, I did not feel assured of success until I had the good fortune to obtain the coöperation of my friend, Don Pascual de Gayangos, Professor of Arabic in the University of Madrid. This eminent scholar was admirably qualified for the task which he so kindly undertook; since, with a remarkable facility--such as long practice only can give--in deciphering the mysterious handwriting of the sixteenth century, he combined such a thorough acquaintance with the history of his country as enabled him to detect, amidst the ocean of manuscripts which he inspected, such portions as were essential to my purpose. With unwearied assiduity he devoted himself to the examination of many of the principal collections, both in England and on the Continent. Among these may be mentioned the British Museum and the State-Paper Office, in London; the Library of the Dukes of Burgundy, in Brussels; that of the University of Leyden; the Royal Library, at the Hague; the Royal Library of Paris, and the Archives of the Kingdom, in the Hôtel Soubise; the Library of the Academy of History, the National Library at Madrid, and, more important than either, the ancient Archives of Simancas, within whose hallowed precincts Señor Gayangos was one of the first scholars permitted to enter.