The substance of the winds is too thin for human eyes, their written language is too difficult for human minds, and their spoken language mostly too faint for the ears.

Muir treats wind as a kind of living presence with its own “substance” and “languages,” yet one that largely exceeds human sensory and intellectual limits. The line underscores a recurring theme in his nature writing: the natural world is not merely scenery but an active, communicative reality whose meanings are only partially available to us. By framing wind’s “written” and “spoken” language as difficult or faint, he suggests humility before nature and invites attentive, patient perception—an ethic of listening and reading the landscape even when full comprehension is impossible.