But, looking, I presently saw something stirring within the shadow: greyish billowy movements, one above another, and then two luminous disks—like eyes. Then something resembling a little grey snake, about the thickness of a walking stick, coiled up out of the writhing middle, and wriggled in the air towards me—and then another.

How does the author create an aesthetic impact in the excerpt?

through realistic dialogue
through a comforting tone
through scientific explanation
through colorful description