For instance, if a little class are to be taught simple addition, after the process is once explained, which may be done, perhaps, in two or three lessons, they will need many days of patient practice to render it familiar, to impress it firmly in their recollection, and to enable them to work with rapidity.

Now this object must be steadily pursued.

It would be very unwise for the teacher to say to himself, My class are tired of addition; I must carry them on to subtraction, or give them some other study.

It would be equally unwise to keep them many days performing example after example in monotonous succession, each lesson a mere repetition of the last.

He must steadily pursue his object of familiarizing them fully with this elementary process, but he may give variety and spirit to the work by changing occasionally the modes.