A work to create some surprise, coming from Spain, is the _Persecution of the Spanish Protestants by Philip the Second_, by Don ADOLPHO DE CASTRO. The name of Castro is honorably distinguished in Spanish literature. The present author is a grandson, we believe, of Rodriguez de Castro, who wrote the BIBLIOTECA ESPAÑOLA. He displays abilities and a temper suitable for the task he attempted; he has joined to careful and intelligent research a bravery of characterization which quite relieves his work from the censures which belong to most Spanish compositions of its class. That he could print in Madrid a work in which statecraft and ecclesiastical persecutions are so frankly dealt with, is a fact of more significance than a dozen such revolutions as have vexed the slumbers of other states. In Spain, above all countries, the spread of a taste for historical studies must be regarded as pregnant with important consequences. It shows that the barriers of ignorance and self-conceit, which have so long isolated that country from the rest of Europe, are beginning to be effectually broken down. To the common Protestant reader, indeed, De Castro's work will appear studiously moderate, or perhaps timid. But it should be remembered that it was written for a public which is four or five centuries behind our own, in all that constitutes true liberty and enlightenment; and what would appear most gratuitous cowardice here may easily enough be remarkable courage in Spain. To speak in favor of Protestantism at all, still more to become the biographer of the Protestant martyrs, is an undertaking which demands from a Spaniard, even of the present day, no ordinary amount of resolution. And we should be by no means surprised to hear that De Castro has been, in one way or another, made to pay some penalty of his rash enterprise. That it is both a dangerous and an unpopular one is manifest from the caution with which historical as well as religious topics are treated. Compiling what we cannot better characterize than as a Spanish supplement to Fox's "Book of Martyrs," the author nowhere professes himself a Protestant. And the slow and gradual way in which he unmasks the character of Philip II., shows how haughty and sensitive are the public whom he has undertaken to disabuse of a portion of the inveterate pride and prejudice which they nourish on all subjects affecting their church or their country. On the whole, however, though the Protestant reader will occasionally desiderate a little more warmth and indignation when chronicling such atrocities, we should say that the book rather gains than loses by this studied moderation both in tone and opinions. It certainly gains in dignity and impressiveness; and it is vastly better adapted to make its way with the author's countrymen, than if he had betrayed at the outset a sectarian bias, which would have revolted them, before they had time to make acquaintance with the sad and sanguinary events of which he is the historian.