184 PSYCHOLOGY AND PREACHING
the thought, should in a general way correspond to the longer wave what we have called a minute wave, though the phrase does not indicate that it is just a minute in length. And so the discourse should in a general way answer to what we have called, for want of a better designa tion, the hour wave, though it should not be forgotten that the phrase does not mean that it should be exactly an hour long, but simply that it can be measured only in terms of the hour. But should the discourse occupy the whole length of this wave? If it does, it will end with the down ward dip of the wave, and the address which concludes with the attention of the hearers relaxed will be to a large extent ineffective. If the discourse must be a lengthy one, and especially when delivered to a popular audience, it should be broken somewhere near the middle by something divert ing and relaxing. If the audience is composed of persons who have formed the habit of giving long-continued close attention to the subject matter of the discourse or matters related thereto, one may reasonably calculate upon holding their sustained attention to the end; but not otherwise. In preaching and all forms of popular discourse, an address of such length, unless broken in half by a few moments of diversion and relaxation, will inevitably produce weariness, and probably disgust. It is not an accident that for serious discourses such as sermons to popular audiences a conven tional limit of about thirty minutes has been set. It is de manded by the laws of the attention. A discourse of this character should occupy only the upward swell of the longer attention wave. Nor is it an accident that popular lec tures, which are usually at least an hour long, are required to be interspersed with diverting passages, even when their aim is instruction. If they are intended to be simply enter taining, i.e., if they appeal chiefly or exclusively to the emo tions of the audience, they should consist not entirely of humour or pathos, but of alternations of the two ; for the normal human mind soon tires of humour or pathos alone,
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