It is easy to work on the emotions of a little child and thoughtless persons may find it amusing but it is a serious matter, for it has an injurious effect upon his nerves. Ghost stories and books which inspire fear of the supernatural often do much harm to imaginative children. The boundless curiosity of the child may be aroused and stimulated so that he gets to know himself and the world about him in a way that furnishes him with constant and delightful employment. The growth of his mind is rapid and healthful, because he is reaching out to comprehend and verify and apply to his own purposes the knowledge that he derives from books and that which he obtains from observation. It is not easy to realize the ignorance of children. Dr. G. Stanley Hall found by experiments with a large number of six-year-olds in Boston, that 55 percent did not know that wooden things are made from trees. The world is strange to them; they must grope their way, they are attracted by the bright, the flashy, the sensational, and their tastes will develop in these directions unless they are taught better. Grown-ups estimate in terms of previous experience; the child has had little previous experience to which to refer. Edward Thring says: "The emptiness of a young boy's mind is often not taken into account, at least emptiness so far as all knowledge in it being of a fragmentary and piecemeal description, nothing complete. It may well happen that an intelligent boy shall be unable to understand a seemingly simple thing, because some bit of knowledge which his instructor takes it for granted he possesses, and probably thinks instinctive, is wanting to fill up the whole."