The sonnet in iambic pentameter is probably the most familiar form in English poetry. A traditional sonnet has fourteen lines and a rhyme scheme. Pretty much all of the great poets before the twentieth century tried their hand at it at some point. Throughout his career, Wordsworth wrote a number of great sonnets, including "Composed Upon Westminster Bridge" earlier in his career. Compared to that poem, "Mutability" seems more formal, you might even say a tad stuffy.
The poem’s rhyme scheme is ABBA ACCA DAC DCA. It is an Italian and not a Shakespearean sonnet – notice the lack of a rhyming couplet at the end. Part of the reason for the poem’s formal sound might be the relative strictness of the iambic pentameter. Before you fall asleep at your computer, let us explain: "iambic" refers to the pattern of unstressed and stressed syllables. One iamb is an unstressed, followed by a stressed syllable: da-DUM. "Pentameter" tells you how many iambs you'll find per line. "Penta" means five – so there are five iambs per line. Iambic pentameter. Here's an example:
From low | to high | doth dis|-so-lu|-tion climb, (line 1)
Italian sonnets are divided into roughly eight lines and six lines, called an octet and a sestet. The rhyme scheme of "Mutability" follows this division, but, thematically, the second half of the poem begins with the discussion of the falling tower.