The triplet and alexandrine are not universally approved. Swift always censured them, and wrote some lines to ridicule them. In examining their propriety, it is to be considered that the essence of verse is regularity, and its ornament is variety. To write verse, is to dispose syllables and sounds harmonically by some known and settled rule; a rule, however, lax enough to substitute similitude for identity, to admit change without breach of order, and to relieve the ear without disappointing it. Thus a Latin hexameter is formed from dactyls and spondees, differently combined; the English heroick admits of acute or grave syllables, variously disposed. The Latin never deviates into seven feet, or exceeds the number of seventeen syllables; but the English alexandrine breaks the lawful bounds, and surprises the reader with two syllables more than he expected.
The effect of the triplet is the same: the ear has been accustomed to expect a new rhyme in every couplet; but is on a sudden surprised with three rhymes together, to which the reader could not accommodate his voice, did he not obtain notice of the change from the braces of the margins. Surely there is something unskilful in the necessity of such mechanical direction.
Considering the metrical art simply as a science, and, consequently, excluding all casualty, we must allow that triplets and alexandrines, inserted by caprice, are interruptions of that constancy to which science aspires. And though the variety which they produce may very justly be desired, yet, to make our poetry exact, there ought to be some stated mode of admitting them.
But till some such regulation can be formed, I wish them still to be retained in their present state. They are sometimes grateful to the reader, and sometimes convenient to the poet. Fenton was of opinion, that Dryden was too liberal, and Pope too sparing, in their use.
The rhymes of Dryden are commonly just, and he valued himself for his readiness in finding them; but he is sometimes open to objection.
It is the common practice of our poets to end the second line with a weak or grave syllable:
Together o'er the Alps methinks we fly,
Fill'd with ideas of fair Italy.
Dryden sometimes puts the weak rhyme in the first:
Laugh all the powers that favour tyranny,
And all the standing army of the sky.
Sometimes he concludes a period or paragraph with the first line of a couplet, which, though the French seem to do it without irregularity, always displeases in English poetry.