His published letters are an invaluable treasure: they abound with wise maxims of sound policy, and curious discussions on points arising on Roman or Belgic jurisprudence. Many points of sacred and profane learning, and particularly of the civil and canon law, are treated in them with equal learning and taste. For the perfect understanding of them, the letters of the correspondents of Grotius should be perused: they are principally to be found, in the _Præstantium et Eruditorum Virorum Epistolæ Ecclesiasticæ et Theologicæ_, published at Amsterdam in 1684. A critical account of the Letters of Grotius, executed with great taste and judgment, is inserted in the first volume of the _Bibliotheque Universelle et Historique_.[041] [Sidenote: X. 6. Other Works of Grotius.] It is acknowledged that the letters of Grotius, are written in the finest latinity, and contain much valuable information; but the point, the sprightliness, the genius, the vivid descriptions of men and things, which are so profusely scattered over the letters of Erasmus, are seldom discoverable in those of Grotius. A man of learning would have been gratified beyond measure, by the profound conversations of Grotius and Father Petau: but what a treat must it have been, to have assisted with one, two, or three good listeners, at the conversations between Erasmus and Sir Thomas More! CHAPTER. XI. GROTIUS.--AS AMBASSADOR FROM THE KINGDOM OF SWEDEN TO THE COURT OF FRANCE. 1634--1645. The embassy of Grotius is connected with an important period in the history of the War of Thirty years. This celebrated war was principally caused by the religious disputes of the sixteenth century. Very soon after Luther's first attack on the See of Rome, the Reformation was established in Saxony, Livonia, Prussia, and Hesse-cassell; in many imperial towns; in Friezland and Holland; in several of the Swiss Cantons; in Pomerania, Mecklenburgh, Anhalt; Sweden, Denmark, Norway; England, and Scotland. Its progress in Germany is particularly connected with the subject of these pages. [Sidenote: Embassy of Grotius in the Court of France.]