On the cover of this curious epistle the emperor indorsed a direction to his son, to show it to no living person; but if he found himself ill at any time, to destroy the letter, or seal it up under cover to him. It would, indeed, have edified those courtiers, who fancied they stood highest in the royal favor, to see how, to their very depths, their characters were sounded, and how clearly their schemes of ambition were revealed to the eye of their master. It was this admirable perception of character which enabled Charles, so generally, to select the right agent for the execution of his plans, and thus to insure their success. The letter from Palamos is one among many similar proofs of the care with which, even from a distance, Charles watched over his son's course, and endeavored to form his character. The experienced navigator would furnish a chart to the youthful pilot, by which, without other aid, he might securely steer through seas strange and unknown to him. Yet there was little danger in the navigation, at this period; for Spain lay in a profound tranquillity, unruffled by a breath from the rude tempest, that, in other parts of Europe, was unsettling princes on their thrones. A change was now to take place in Philip's domestic relations. His magnificent expectations made him, in the opinion of the world, the best match in Europe. His father had long contemplated the event of his son's marrying. He had first meditated an alliance for him with Margaret, daughter of Francis the First, by which means the feud with his ancient rival might be permanently healed. But Philip's inclination was turned to an alliance with Portugal. This latter was finally adopted by Charles; and, in December, 1542, Philip was betrothed to the Infanta Mary, daughter of John the Third and of Catharine, the emperor's sister. She was, consequently, cousin-german to Philip. At the same time, Joanna, Charles's youngest daughter, was affianced to the eldest son of John the Third, and heir to his crown. The intermarriages of the royal houses of Castile and Portugal were so frequent, that the several members stood in multiplied and most perplexing degrees of affinity with one another. Joanna was eight years younger than her brother. Charles had one other child, Mary, born the year after Philip. She was destined to a more splendid fortune than her sister, as bride of the future emperor of Germany. Since Philip and the Portuguese princess were now both more than sixteen years old, being nearly of the same age, it was resolved that their marriage should no longer be deferred. The place appointed for the ceremony was the ancient city of Salamanca. [Sidenote: MARRIES MARY OF PORTUGAL.]