At other times it is better to trust for the serial interest to history,--to study the evolution of a nation as before of a man. The wondrous tale of the rise of the Hebrews from Abraham, their metamorphosis under Moses, their consolidation under judges, their expansion under kings, their division, their downfall, their restoration, their subjugation, their new birth in Him who was before Abraham,--this story may be made to have a deep and constant serial interest. Of course, with either the biographical or historical serial plan, great pains must be taken with that bugbear of the average teacher,--what the lesson-helps call intervening events, but many a scholar calls intervening mystifications. Often fully half the lesson-time should be given to them. Usually the antecedents they contain are absolutely necessary for an understanding of the lesson,--text, persons, and principles. With them you teach history; without, episodes. They mean work, to be sure; but all unifying and solidifying means work. At still other times or with other classes it is well to let the serial interest center around principles. Treat one group of lessons as illustrating the manly or unmanly qualities; consider another group primarily as a commentary on truth and falsehood; let your binding topic for another set be "What is True Religion?" "Sin and Salvation," "Serving and Served," "Success and Failure,"--how many lessons could be clustered naturally about these topics! Children are characteristically philosophers, and a treatment of Sunday-school lessons as illustrating different phases of some great truth is a method very attractive to them. "What does the Bible teach about truth-telling, about penalty for sin, about the conditions of happiness?" Sunday-school scholars should be ready to answer such questions, not by haphazard impromptus, but by a careful presentation of events, characters, and sayings bearing on each point, and representing the whole Bible. Another excellent way of binding lessons together is by the scholars themselves. As I said, however the lessons change, the scholars remain the same, with the same prominent troubles, faults, and needs. Both they and you should know what these are. I often have scholars who bring up, Sunday after Sunday, in connection with topics the most diverse, the same questions, which are evidently stumbling-blocks to their minds and lives. These are usually practical matters wherein the Christian imperatives are strangely incongruous with worldly habits, such as the choice of a calling, absolute frankness of speech, public testimony for Christ, the careful observance of the Sabbath, sharp competition in trade. These are too big questions to be settled in a few minutes, and young folks who are seized by them in earnest have found for themselves a serial interest which will last for some time.