How many layer is our atmosphere

2read this passage from "the raven." what is puzzling the speaker in this stanza? 60% but the raven still beguiling my sad fancy into smiling, straight i wheeled a cushioned seat in front of bird, and bust and door then, upon the velvet sinking, i betook myself to linking fancy unto fancy, thinking what this ominous bird of yore- what this grim, ungainly, ghastly, gaunt and ominous bird of yore meant in croaking "nevermore." s and what the raven's message is why the raven came to visit where the raven came from how the raven got into his room