PRINCE ROBERT, of Bavaria, was born in 1619. His father, Frederic V., elector palatine, had rendered himself an exile by an unsuccessful attempt to seize upon the crown of Bohemia, which entailed upon his son the reverses of his own evil fortune. His mother was Elizabeth, eldest daughter of James I. of England, and by his connection with the British throne the youth resolved to win his way to fame, and perhaps to fortune. Of a restless, active disposition, that had little known the restraints of any regular system of educational discipline, he already had his eye fixed upon the civil wars that were then desolating England, and with a thirst for the fortunes of the soldier, he sought and obtained the command of a regiment of cavalry from his uncle Charles I. of England. He took Hereford, Lichfield, and Cirencester, and shared in the battles of Worcester, Edgehill, and Chalgrove Field. In these engagements he had given proof of much rash courage and of daring impetuosity, but he was found to be destitute of the prudence of the soldier, and was entirely wanting in military sagacity. The king, pleased probably with his rashness, which he trusted to time to bring into subjection to his will, created him a Knight of the Garter and made him Duke of Cumberland. He took Bristol, scattered the parliamentary forces at Newark; but at Long Marston Moor, Oliver Cromwell and his Ironsides compelled him ignominiously to flee. Prince Rupert did not lose confidence by this defeat, nor did the king's reliance on him diminish. He was made general of all the king's troops; he took Leicester; he swept down upon the Ironsides at Naseby; but his rashness, as usual, proved his ruin. He hastened to Bristol to prepare that city to resist an attack, but betrayed such an entire want of strategical skill, and gave such proofs of pusillanimity, that not only was the place taken by the triumphant enemy, but Charles I., having lost all patience with his favourite, stripped him of his command and deprived him of his countenance. But Prince Rupert being a needy man, of great versatility and very adventurous, resolved to try his fortune upon the sea, seeing she had deserted him by land. He accordingly obtained command of the fleet in 1648, but had Blake out upon him before many months, who pursued him to Kinsale, to Lisbon, to Carthagena, until, Rupert having sunk and captured some English merchantmen at Malaga, the little admiral burnt and destroyed almost his whole fleet, and compelled him to take refuge with two or three ships in the West Indies, where he for some time supported himself by piracy. Returning across the Atlantic, he took refuge in a French port, sold his ships to the French government, and went for a time at large throughout France. On the restoration of Charles II., he again sought the English court, and having now blustered out his youthful impetuosity, he was again appointed to a command under the Duke of York. In 1673 he was entrusted with the command of the fleet, but found it so ill equipped and so weakly manned that he chose to return home rather than face the enemy in such a condition. Prince Rupert had now completed the active part of his life. As governor of Windsor, he occupied his leisure, according to the fashion of the times, with painting and engraving, with mechanical and chemical experiments. He attained to some distinction in the engraver's art, and is generally supposed to have been the inventor of mezzotinto. This is, however, a mistake, as the invention belongs to a German named Siegen, who, having fallen upon the art in the year 1642, showed it to Prince Rupert, whom he met at Brussels in 1655 or 1656. (Laborde's Histoire de la Gravure en Maniere Noire.) He died at Spring Gardens on the 29th of November 1682, and was interred with great magnificence in Henry VII.'s chapel, Westminster.

Prince Rupert is believed to be the inventor of pinchbeck or prince's metal, and of those curious glass bubbles known as "Rupert's drops" (see Annealing), which, as Lord Macaulay remarks, "have long amused children and puzzled philosophers."