Sec. 54. There is one peculiarity of poetry conducing much to its effect--the peculiarity which is indeed usually thought its characteristic one--still remaining to be considered: we mean its rhythmical structure. This, improbable though it seems, will be found to come under the same generalization with the others. Like each of them, it is an idealization of the natural language of strong emotion, which is known to be more or less metrical if the emotion be not too violent; and like each of them it is an economy of the reader's or hearer's attention. In the peculiar tone and manner we adopt in uttering versified language, may be discerned its relationship to the feelings; and the pleasure which its measured movement gives us, is ascribable to the comparative ease with which words metrically arranged can be recognized. Sec. 55. This last position will scarcely be at once admitted; but a little explanation will show its reasonableness. For if, as we have seen, there is an expenditure of mental energy in the mere act of listening to verbal articulations, or in that silent repetition of them which goes on in reading--if the perceptive faculties must be in active exercise to identify every syllable--then, any mode of so combining words as to present a regular recurrence of certain traits which the mind can anticipate, will diminish that strain upon the attention required by the total irregularity of prose. Just as the body, in receiving a series of varying concussions, must keep the muscles ready to meet the most violent of them, as not knowing when such may come; so, the mind in receiving unarranged articulations, must keep its perceptives active enough to recognize the least easily caught sounds. And as, if the concussions recur in a definite order, the body may husband its forces by adjusting the resistance needful for each concussion; so, if the syllables be rhythmically arranged, the mind may economize its energies by anticipating the attention required for each syllable. Sec. 56. Far-fetched though this idea will perhaps be thought, a little introspection will countenance it. That we do take advantage of metrical language to adjust our perceptive faculties to the force of the expected articulations, is clear from the fact that we are balked by halting versification. Much as at the bottom of a flight of stairs, a step more or less than we counted upon gives us a shock; so, too, does a misplaced accent or a supernumerary syllable. In the one case, we _know_ that there is an erroneous preadjustment; and we can scarcely doubt that there is one in the other. But if we habitually preadjust our perceptions to the measured movement of verse, the physical analogy above given renders it probable that by so doing we economize attention; and hence that metrical language is more effective than prose, because it enables us to do this.