Gary Snyder writes that his poetic rhythms derive from the rhythym of the physical work he was doing at the time of writing. As a young poet, this work was "riprap," "the daily trail-crew work of picking up and placing granite stones in tight cobble patterns on hard slab." This prosody is seen described in the poem "Riprap":
"Lay down these words/Before your mind like rocks./ placed solid, by hands/In choice of place, set/Before the body of the mind /in space and time." These lines show Snyder's desire to build lines up with short, substantive words. The words are fit together by the recurring sound patterns; the last two lines of the quoted section contain the sonic key to the poem: the long i, the long a and the ahh sound of body (and rock). Snyder's craft is patient and deliberate, the kind of effort needed to build a road up a mountain.
In the longer "Myths and Texts," his rhthyms reflect the tranquility of working on a mountain look out, the occasional heave of attaching logs to tractors, and the chants of Great Basin Indians. Not that riprap in discarded: he still considers "[p]oetry a riprap on the slick rock of metaphysics." We still see the careful constructed lines of "tough, simple, short words, with the complexity far beneath the surface texture. However, he also delves into more a traditionally meditative mode: "One moves continually with the consciousness/of that other, totally alien, non-human.../Attentive to the real-world flesh and stone." This phrase subtly echoes the common expression 'flesh and bone.' In Snyder, "Bones & flesh knit into the rock." John Muir is a figure in "Myths and Texts" who becomes both flesh and stone, melding with the mountain he's climbing. He describe Muir's paralyzing fear, clinging to the rock face and imagining falling into the chasm. After the fear passes, he perceives the rock in detail and his "limbs moved with a positiveness and precision" that he "seemed to have nothing at all to do" with. It is as if his flesh self did fall, and his stone self brought him up the cliff. Near the end of the sequence, there's a sort of reverse riprap. Human improvements, like the flesh's desire to know for knowledge, is not permanent. While the poet sits on his mountain lookout, he observes "It's all falling or burning--/rattle of boulders/steady dribbling of rocks down cliffs." Snyder has a comprehensive poetic that accounts for the "two sources of human knowledge--symbols and sense-impressions." Often they are the same: in the poems discussed here, he creates symbolic discourse out of the sense-impressions of labor and observations. A man can create roads that up, but the mountain will push the rocks back down-- "It's all falling or burning."
Further reading: the complete Myths and Texts