You assign to a class of little girls a subject of composition, requesting them to copy their writing upon a sheet of paper, leaving a margin an inch wide at the top, and one of half an inch at the sides and bottom.

The class take their seats, and, after a short time, one of them comes to you, saying she does not know how long an inch is.
"Don't you know any thing about it ?" "No, sir, not much." "Should you think _that_ is more or less than an inch ?" (pointing to a space on a piece of paper much too large).
"More." "Then you know something about it.

Now I did not tell you to make the margins _exactly_ an inch and half an inch, but only as near as you could judge ?" "Would _that_ be about right ?" asks the girl, showing a distance.
"I must not tell you, because, you know, I never in such cases help individuals; if that is as near as you can get it, you may make it so." It may be well, after assigning a lesson to a class, to say that all those who do not distinctly understand what they have to do may remain after the class have taken their seats, and ask: the task may then be distinctly assigned again, and the difficulties, so far as they can be foreseen, explained.
By such means these sources of interruption and difficulty may, like the others, be almost entirely removed.

Perhaps not altogether, for many cases may occur where the teacher may choose to give a particular class permission to come to him for help.

Such permission, however, ought never to be given unless it is absolutely necessary, and should never be allowed to be taken unless it is distinctly given.
4.