Limitations of imagination.--Since childhood is the age of imagination, we might naturally expect that it would be no trouble to secure ready response from the child's imagination. But we must not assume too much about the early power of imagination. It is true that the child's imagination is _ready and active_; but it is not yet ready for the more difficult and complex picturing we sometimes require of it, for imagination depends for its material on the store of _images_ accumulated from former experience; and images are the result of past observation, of percepts, and sensory experiences. The imagination can build no mental structures without the stuff with which to build; it is limited to the material on hand. The Indians never dreamed of a heaven with streets of gold and a great white throne; for their experiences had given them no knowledge of such things. They therefore made their heaven out of the "Happy Hunting Grounds," of which they had many images. Many Chicago school children who were asked to compare the height of a mountain with that of a tall factory chimney said that the chimney was higher, because the mountain "does not go straight up" like the chimney. These children had learned and recited that a mountain "is an elevation of land a thousand or more than a thousand feet in height," but their imagination failed to picture the mountain, since not even the smallest mountain nor a high hill had ever been actually present to their observation. Small wonder, then, that Sunday school children have some trouble, living as they do in these modern times, to picture ancient times and peoples who were so different from any with which their experience has had to deal! Guiding principles.--The skillful teacher knows how to help the child use his imagination. The following laws or principles will aid in such training: 1. _Relate the new scene or picture with something similar in the child's experience._ The desert is like the sandy waste or the barren and stony hillside with which the children are acquainted. The square, flat-topped houses of eastern lands have their approximate counterpart in occasional buildings to be found in almost any modern community. The rivers and lakes of Bible lands may be compared with rivers and lakes near at hand. The manner of cooking and serving food under primitive conditions was not so different from our own method on picnics and excursion days. While the life and work of the shepherd have changed, we still have the sheep. The walls of the ancient city can be seen in miniature in stone and concrete embankments, or even the stone fences common in some sections.