“The same tendency that urges the boy to seek knowledge on the mountain and in the valley, attracts and holds him to the plain. Here he makes a garden, there he represents the course of the river, and studies the effect of the presence of water … here he has dammed up the water to form a pool.… He is particularly fond of busying himself with clear running water and with plastic materials. In these the boy who seeks self-knowledge beholds his soul as in a mirror. These employments are to him an element of his life, for now, because of a previously acquired sense of power he seeks to control and master new material. Everything must submit to his constructive instinct; there in that heap of earth he digs a cellar and on it he places a garden and a bench. Boards, branches and poles must be made into a hut, the deep, fresh snow must be rolled up to form the walls and ramparts of a fort, and the rough stones on the hill are heaped together to form a castle.… And thus each one soon forms for himself his own world; for the feeling of his own power requires and conditions also the possession of his own space and his own material belonging exclusively to him. Whether his kingdom, his province, his estate, as it were, be a corner of the yard, or of the house, or whether it be the space of a box, the human being must have at this stage an external point to which he refers all his activities, and this is best chosen and provided by himself.”--_E., p. 106._ And here, just when he is emphasizing the fast developing consciousness of self, with its demand for its own space and its own material, Froebel brings out the strength of the social instinct in boyhood. It is here that he points out that this effort to construct has a uniting, not a separating, tendency. Continuous with the last quotation comes: “When the space to be filled is extensive, when the province to be ruled is large, when the whole to be represented is composed of many parts, then brotherly union of those who are of one mind is displayed. And when those who are of one mind meet and put their hearts into the same effort, then either the work already begun is extended or begun again as a joint production.”--_E., p. 107._ Froebel describes such joint work first in the Keilhau schoolroom--his own phrase is “education room”--where the younger boys are using building blocks, sand, sawdust, and moss, which they have brought in from the forest around and then among the older boys.