Secondly, I argue from the effects of metre. As far as metre acts in and for itself, it tends to increase the vivacity and susceptibility both of the general feelings and of the attention. This effect it produces by the continued excitement of surprise, and by the quick reciprocations of curiosity still gratified and still re-excited, which are too slight indeed to be at any moment objects of distinct consciousness, yet become considerable in their aggregate influence. As a medicated atmosphere, or as wine during animated conversation, they act powerfully, though themselves unnoticed. Where, therefore, correspondent food and appropriate matter are not provided for the attention and feelings thus roused, there must needs be disappointment felt;--like that of leaping in the dark from the last step of a staircase, when we had prepared our muscles for a leap of three or four. The discussion on the powers of metre, in the Preface, is highly ingenious, and touches at all points on truth. But I cannot find any statement of its powers considered abstractly and separately. On the contrary, Mr. Wordsworth seems always to estimate metre by the powers which it exerts during (and, as I think, in consequence of) its combination with other elements of poetry. Thus the previous difficulty is left unanswered, what the elements are with which it must be combined in order to produce its own effects to any pleasurable purpose.... For any poetic purposes, metre resembles (if the aptness of the simile may excuse its meanness) yeast, worthless or disagreeable by itself, but giving vivacity and spirit to the liquor with which it is proportionally combined.... Metre in itself is simply a stimulant of the attention, and therefore excites the question, Why is the attention to be thus stimulated? Now the question cannot be answered by the pleasure of the metre itself; for this we have shown to be conditional, and dependent on the appropriateness of the thoughts and expressions to which the metrical form is superadded. Neither can I conceive any other answer that can be rationally given, short of this: I write in metre, because I am about to use a language different from that of prose.... Thirdly, I deduce the position from all the causes elsewhere assigned which render metre the proper form of poetry, and poetry imperfect and defective without metre. Metre, therefore, having been connected with poetry most often, and by a peculiar fitness, whatever else is combined with metre must, though it be not itself essentially poetic, have nevertheless some property in common with poetry, as an intermedium of affinity. (COLERIDGE: _Biographia Literaria_, chap. xviii.)