Albert's mental development now proceeded apace. In his seventeenth year he began a careful study of German literature and German philosophy. He set about, he told his tutor, "to follow the thoughts of the great Klopstock into their depths--though in this, for the most part," he modestly added, "I do not succeed." He wrote an essay on the "Mode of Thought of the Germans, and a Sketch of the History of German Civilisation," "making use," he said, "in its general outlines, of the divisions which the treatment of the subject itself demands," and concluding with "a retrospect of the shortcomings of our time, with an appeal to every one to correct those shortcomings in his own case, and thus set a good example to others." Placed for some months under the care of King Leopold at Brussels, he came under the influence of Adolphe Quetelet, a mathematical professor, who was particularly interested in the application of the laws of probability to political and moral phenomena; this line of inquiry attracted the Prince, and the friendship thus begun continued till the end of his life. From Brussels he went to the University of Bonn, where he was speedily distinguished both by his intellectual and his social activities; his energies were absorbed in metaphysics, law, political economy, music, fencing, and amateur theatricals. Thirty years later his fellow--students recalled with delight the fits of laughter into which they had been sent by Prince Albert's mimicry. The verve with which his Serene Highness reproduced the tones and gestures of one of the professors who used to point to a picture of a row of houses in Venice with the remark, "That is the Ponte-Realte," and of another who fell down in a race and was obliged to look for his spectacles, was especially appreciated.