Probably obvious to anyone familiar with nature or Mt. Ranier (or perhaps just to any non-thick casual reader of the poem) but the poem’s mentions of “glass” refer to the glaciers on Mt. Ranier.
…”Composed of glass that bends, a much needed invention”
…”The glassy octopus, symmetrically pointed.”
The word glacier comes from French glace, meaning ice, though interestingly English “glass” does not come from glace but has a root meaning of shine. (The root meaning of French “glace” is cold, freezing.)
The other mention of glass in the poem, of which one may wonder in a broad fashion is “…the spotted ponies with glass eyes, brought up on frosty grass and flowers and rapid draughts of ice water.”
We are told that the spotted ponies can climb the mountain, so (if the mountain can be equated with the poem itself, and climbing the mountain with understanding the poem) one imaginative reading would be that these “glass eyes” are spectacles and that these ponies are readers of a special sort.
.i`` * ^ / . . . . . ` `~ 