The most striking quality of Shelley's poetry meets our attention once, in the play of ever-changing emotion through his lines. When he called himself "A pard-like Spirit beautiful and swift," he characterized the spirit of his poetry, with its ever-shifting imagery, and its pulsing, leaping rhythms continually falling into new and unexpected adjustments of difficult stresses, but always resolving themselves into a wonderful coherency of thought and form which produces the effect of strange and beautiful music. He builds up large rhythm-forms in what we may call the phrasing of his lines, using the term in a musical sense, and over these large waves play the verse-waves in a vast variety of subtle adjustments. As striking an illustration as we could find of this, lies in that magnificently descriptive line from Alastor – Of wave ruining on wave, and Blast on blast. 327.