The bias of fashion would soon be modified by the precedence of its leaders, as in Prussia, where the royal family set a good example by educating their princes (in addition to the inevitable military training) in the by-trade of some mechanical accomplishment (carpentry, sculpture, bookbinding, etc.), the choice of handicraft being optional with the pupil. No model residence should be deemed complete without a polytechnic workshop, furnished with a panoply of apparatus for the practice of all sorts of amateur chemical and mechanical pursuits—a plan by which the Hungarian statesman-author, Maurus Jockar, has banished the specter of ennui from his hospitable country seat. His private hobby is Black Art, as he calls his experiments in recondite chemistry, but any one of his guests is welcome to try his hand at wood-carving, glass-painting, metallurgy, or any of the more primitive crafts, for which the laboratory furnishes an abundance of apparatus. Private taste might, of course, modify the details of that plan, and even without regard to eventual results, its proximate benefits if once known would alone insure its general adoption in the homes of the ennui-stricken classes. The educational advantages of mechanical training, though, can, indeed, hardly be overrated. A scholar with nerveless arms and undextrous hands is as far from being a complete man as a nimble savage with an undeveloped brain. II.—MENTAL MAXIMS. CHAPTER VI. KNOWLEDGE. A.—LESSONS OF INSTINCT.