Failing this point of departure, all education and instruction would be _impossible_, and the school _useless_. Another difficulty is that of economizing the powers of the pupils, that is to say, utilizing them to the utmost without wasting them. How much rest is necessary? How long should any particular work be carried on? Perhaps ten minutes' rest may be necessary after the first three-quarters of an hour of occupation; but after another three-quarters of an hour, a pause of fifteen minutes may be required, and so on throughout the day; finally, a quarter of an hour's rest may be needed after ten minutes' occupation. But what instruction is best adapted to the powers of a child during the various hours of the day? Is it best to begin with mathematics or with dictation? At what hours will the child be most inclined to exercise his powers of imagination, at 9 in the morning or at 11? Other anxieties must assail a perfect teacher! How should he write on the blackboard so that the children seated at a distance may see? for if they do not see his work is of no avail. And how much light shall fall upon the blackboard, in order that all may see clearly the white characters on the black surface? Of what size should be the script specially chosen by the master to suit distant vision? This is a serious matter, because if the child, obliged by discipline to look and learn from a distance, should put too great a strain upon his powers of visual accommodation, he may in time become short-sighted; then the teacher would have manufactured a blind person. A serious matter indeed! * * * * * What consideration has ever been given to the state of anxiety of such a teacher? To get some idea of his anxiety we may think of a young wife about to become a mother, who should set herself such problems as the following: how can I create an infant, if I know nothing of anatomy; how can I form its skeleton? I must study the structure of the bones carefully. I must then learn how the muscles are attached; but how will it be possible to put the brain into a closed box? And must the little heart go on beating continually until death? Is it possible that it will not weary? In like fashion, she might ponder thus over her new-born babe: it is evident that he will not be able to walk if he does not first of all understand the laws of equilibrium; if he is left to himself, he will not be able to understand these till he is twenty; I must therefore prepare to teach him these laws prematurely in order that he may be able to walk as quickly as possible.