The reason is because it is a pure Iambic line, and therefore very vocal; since, if it contained many consonants, as nearly every English line does, they must make most of the previous vowels long by position; and, though accent generally determines the quantity in English, literal quantity enters more into the construction of English verse than is commonly supposed.
I may here observe that the stanza commonly called “Spenserian” is by no means so purely an original invention of that most imaginative poet as is usually represented. The Alexandrine at the close is the only part that is original. I find the germ of Spenser’s stanza very palpably in the old ballet-staves and in the works of two poets who lived fully a century before him, Skelton who styled himself Poet Laureate to Henry VII. and Stephen Hawes who was Gentleman of the Bedchamber to the same monarch. The following stanza is from Skelton’s “Elegy on the death of Henry Percy, fourth Earl of Northumberland:”—it is the ballet-stave of seven, in which was written an enormous quantity of early, but now forgotten, English poetry, and in which Spenser has written his “Ruins of Time,” and Shakspeare his “Rape of Lucrece.”
O cruell Mars, thou dedly god of war!
O dolorous Teusday, dedicate to thy name,
When thou shoke thy sworde so noble a man to mar!
O grounde ungracious, unhappy be thy fame,
Which wert endyed with rede blode of the same!
Most noble earl! O fowle mysuryd grounde
Whereon he gat his fynal dedely wounde!
Down to the end of the fifth line this is precisely the stanza of Spenser. With the addition of two lines, one rhyming with the last, and the other with the fifth, and of two syllables to the closing line, it is literally that stanza. But in fact the latter addition was often made by both Skelton and Hawes, though irregularly, metrical cadence being then imperfectly understood, and both poets being of the “tumbling” school. This poem was probably composed in the year 1490. Skelton died in 1529, and an edition of his poems in black letter appeared in 1568. I take the stanza which follows from a poem of Hawes’s called “The History of Graunde Amoure and la Belle Pucel,” written in 1505 and published in quarto in 1555: