Hopkin's Original Preface (the so-called Author's Preface to the 1918 Edition)

The poems in this book(1) are written some in Running Rhythm, the common rhythm in English use, some in Sprung Rhythm, and some in a mixture of the two. And those in the common rhythm are some counterpointed, some not.

Commentary: Thus, Hopkins neatly devides the domain of English poetry into major rhythmic categories

Running-----------------------Sprung
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no------yes----mixture------yes---------no