When I Heard the Learn'd Astronomer Isolation Quotes
How we cite our quotes: (line)
were ranged in columns before me; (line 2)
If you really wanted to get carried away with symbolism, you might compare those columns to prison bars. At any rate, they represent the kind of artificial order that society opposes on the natural world.
where he lectured with much applause in the lecture-room, (line 4)
We don't learn that the speaker is in a crowded lecture until this point in the poem. He feels alone and isolated despite the crowd. The other people are mentioned indirectly, through their "applause," but otherwise we know nothing about them.