(1) That the sonnet is written in iambic pentameter, and consists of fourteen lines—that number by repeated experimentation having been found the most appropriate for the expression of a single emotional mood.
(2) As an examination of the rimes will show (a b b a a b b a: c d d e c e), there is a natural metrical division at the end of the eighth line. The first eight lines in technical language are called the "octave," the last six lines are called the "sestet." The octave is sometimes said to consist of two quatrains, and the sestet of two tercets.
(3) There is not only a metrical division between the octave and the sestet, but the character of the thought also undergoes a subtle change at that point. It is to be understood, of course, that in the whole poem there must be both unity of thought and mood. Yet, at the ninth line, the thought which is introduced in the octave is elaborated, and presented as it were under another aspect. As Mr. Mark Pattison has admirably expressed it: "This thought or mood should be led up to, and opened in the early lines of the sonnet; strictly, in the first quatrain; in the second quatrain the hearer should be placed in full possession of it. After the second quatrain there should be a pause—not full, nor producing the effect of a break—as of one who had finished what he had got to say, and not preparing a transition to a new subject, but as of one who is turning over what has been said in the mind to enforce it further. The opening of the second system, strictly the first tercet, should turn back upon the thought or sentiment, take it up and carry it forward to the conclusion. The conclusion should be a resultant summing the total of the suggestion in the preceding lines. . . . While the conclusion should leave a sense of finish and completeness, it is necessary to avoid anything like epigrammatic point."
(4) An examination of the rimes again will show that greater strictness prevails in the octave than in the sestet. The most regular type of the octave may be represented by a b b a a b b a, turning therefore upon two rimes only. The sestet, though it contains but six lines, is more liberal in the disposition of its rimes. In the sonnet which we are examining, the rime system of the sestet in c d d e c e—containing, as we see, three separate rimes. In the sestet this is permissible, provided that there is not a riming couplet at the close.
(5) Again, with reference to the rime, it will be observed that the vowel terminals of the octave and the sestet are differentiated. Anything approaching assonance between the two divisions is to be counted as a defect.
(6) It is evident that there is unity both of thought and mood in this sonnet, the sestet being differentiated from the octave, only as above described.
(7) It is almost unnecessary to add that there is no slovenly diction, that the language is dignified in proportion to the theme, and that there is no obscurity or repetition in thought or phraseology.
These rules will appear to the young reader of poetry as almost unnecessarily severe. But it must be remembered that the sonnet is avowedly a conventional form (though in it much of the finest poetry in our language is contained), and as such the conventional laws attaching to all prescribed forms must be observed to win complete success.
Spenser, Shakespeare, and Milton have lent the authority of their great names to certain distinct variations from the rigid Petrarchan type. The peculiarity of Spenser's sonnets is that the rime of the octave overflows into the sestet, thus marring the exquisite balance which should subsist between the two parts, and yielding an effect of cloying sweetness. Although the famous stanza-form which he invented in his "Faerie Queene" has found many imitators, his sonnet innovations are practically unimportant.
The Shakespearean sonnet, on the contrary, must be regarded as a well-established variant from the stricter Italian form. Though Shakespeare's name has made it famous, it did not originate with him. Surrey and Daniel had habitually employed it, and in fact it had come to be recognized as the accepted English form. Its characteristic feature, as the following sonnet from Shakespeare will show, was a division into three distinct quatrains, each with alternating rimes, and closed by a couplet. The transition of thought at the ninth line is usually observed:—