At one of the battles which was fought, the celebrated John Hampden, the man who would not pay his ship money, was slain. He had been a very energetic and efficient officer on the Parliamentary side, and was much dreaded by the forces of the king. At one of the battles between Prince Rupert, Charles's nephew, and the army of the Parliament, the prince brought to the king's camp a large number of prisoners which he had taken. One of the prisoners said he was confident that Hampden was hurt, for he saw him riding off the field before the battle was over, with his head hanging down, and his hands clasping the neck of his horse. They heard the next day that he had been wounded in the shoulder. Inflammation and fever ensued, and he died a few days afterward in great agony. This Prince Rupert was a very famous character in all these wars. He was young and ardent, and full of courage and enthusiasm. He was always foremost, and ready to embark in the most daring undertakings. He was the son of the king's sister Elizabeth, who married the Elector Palatine, as narrated in a preceding chapter. He was famous not only for his military skill and attainments, but for his knowledge of science, and for his ingenuity in many philosophical arts. There is a mode of engraving called mezzotinto, which is somewhat easier of execution than the common mode, and produces a peculiar effect. Prince Rupert is said to have been the inventor of it, though, as is the case with almost all other inventions, there is a dispute about it. He discovered a mode of dropping melted glass into water so as to form little pear-shaped globules, with a long slender tail. These globules have this remarkable property, that if the tip of the tail is broken off ever so gently, the whole flies into atoms with an explosion. These drops of glass are often exhibited at the present day, and are called Prince Rupert's drops. The prince also discovered a very tenacious composition of metals for casting cannon. As artillery is necessarily very heavy, and very difficult to be transported on marches and upon the field of battle, it becomes very important to discover such metallic compounds as have the greatest strength and tenacity in resisting the force of an explosion. Prince Rupert invented such a compound, which is called by his name.