As an illustration of our meaning, we may notice here, that a child who knows what is meant by "sheep," and "the keeping of sheep," of "tilling the ground," and "making an offering to God," &c. is prepared to hear or to read an abridgement of the story of Cain and Abel. We say _an abridgement_ or _first step_, for reasons which shall afterwards be explained. Without a previous knowledge of these several elements of which this story is compounded, he could neither have listened to it with pleasure, nor read it with any degree of profit; but as soon as these are individually familiar, the grouping,--the knowledge of the whole story,--is a matter of ease, and generally of delight. As the story advances, it causes a constant and regular series of groupings on the mind by the imagination, which are at once exquisitely pleasing and permanent. The child, as in a living and moving picture, imagines a man laboriously digging the ground, and another man in a distant field placidly engaged in attending to the wants and the safety of a flock of sheep. He imagines the former heaping an altar with fruits and without fire; and the latter killing a lamb, laying its parts on an altar, while a stream of fire descends from the skies and consumes it. His imagination goes on with increasing interest to picture the quarrel-scene in the field; and he in effect sees the blow given by the club of Cain, that destroyed the life of his brother. All this living and moving scene will be remembered in groups; and these groups will be more or less closely linked together, and will be imagined more or less distinctly as a whole, in proportion to the mental advancement of the particular child.