contrast to the firm and almost indelible impression that results when they have been inked. Similarly, the instruction that boys receive from books, those dumb teachers, is obscure and imperfect, but when it is supplemented by the voice of the teacher (who explains everything in a manner suitable to his hearers), it becomes vivid and makes a deep impression on their minds, so that they really understand what they learn and are conscious that they understand it. Again, printing-ink differs from writing-ink, since it is made, not with water, but with oil (indeed, those who want a very superior ink, use the finest oil and the best charcoal); and, similarly, the voice of a teacher who can teach persuasively and clearly should sink like oil into the pupils’ minds and carry information with it.
17. Finally, the function of the press in printing is performed in schools by discipline, which is in itself sufficiently powerful to ensure that no pupil shirk his studies. Every sheet of paper that is to form part of a book must pass through the press (hard paper needing more, and soft paper less pressure); and, similarly, whoever wishes to learn at a school must be subjected to its discipline. There are three grades of discipline: firstly, perpetual watchfulness; for since we can never put implicit faith in the diligence or innocence of boys (are they not Adam’s brood?) we must keep them continually under our eyes. Secondly, blame, by which those who leave the beaten path must be recalled to the way of reason and obedience. Finally, punishment, which must be employed if exhortation have no effect. All discipline, however, must be used with prudence and with no other object than to induce the pupils to do all their work well.
18. I said that certain processes were necessary, and that these had to be carried out in a certain definite manner. This point deserves a brief investigation.
19. If a certain number of copies of a book is to be printed, that number of sheets is taken at once and printed from the same block, and from each successive block, from the beginning to the end of the book, the same number of
