Even more striking is the difference of rhythmical effect observable in reading, one after the other, a page of Pope's heroic couplets in the Essay on Man, of Keats's same couplets in Endymion, and Browning's same couplets in My Last Duchess.
While the formal pattern remains fixed and inflexible, over its surface may be embroidered variations of almost illimitable subtlety and change; but always the formal pattern must be visible, audible. The poet's skill lies largely in preserving a balance of the artistic principles of variety in uniformity and uniformity in variety. Once he lets go the design, he loses his metrical rhythm and writes mere prose. Once we cease to hear and feel the faint regular beating of the metronome we fail to get the enjoyment of sound that it is the proper function of metre to give. On the other hand, if the mechanical design stands out too plainly, if the beat of the metronome becomes for an instant more prominent than the music of the words, then also the artistic pleasure is gone, for too much uniformity is as deadly to art as too much variety.
The curfew tolls the knell of parting day,
The lowing herd winds slowly o'er the lea,
The plowman homeward plods his weary way,
And leaves the world to darkness and to me.
These verses are regular (as is appropriate for the theme), and vary comparatively little from the formal metrical pattern. The coincidence of prose rhythm and metrical rhythm is almost complete. Yet by means of small subtleties of variation in pause, word order, long and short syllables, Gray always saves the poem from monotony. How far the variations may be carried, how much the ear may be depended upon for rhythmic substitution and syncopation, is determined by many things. Certain lines are unmistakably metrical to all ears and in all positions—such as these verses of Gray's Elegy. Certain lines are generally felt to contain daring variations and yet be successful and effective—such as
The blue Mediterranean, where he lay.
Shelley, Ode to the West Wind.
Myriads of rivulets hurrying thro' the lawn.
Tennyson, Small Sweet Idyl, in The Princess.
Other lines stretch our metrical sense to the breaking point, and according to individual taste we judge them bold or too bold—such as Tennyson's
Take your own time, Annie, take your own time.
Enoch Arden.
or Milton's