When I heard the Learn'd Astronomer
Walt Whitman

When I heard the learn'd astronomer,
When the proofs, the figures, were ranged in columns before me,
When I was shown the charts, the diagrams, to add, divide, and measure them,
When I sitting heard the astronomer where he lectured with much applause in the lecture room,
How soon unaccountable I became tired and sick,
Till rising and gliding out I wander'd off by myself,
In the mystical moist night-air, and from time to time,
Look'd up in perfect silence at the stars.

"When I Heard the Learn'd Astronomer" begins with the repetition of the title, this gives more weight to the first phrase. Beginning to the title we can understand the contest, in which someone is listening an astronomer, probably he will be sitting and with other people.
The verb heard is a perception verb, which gives an idea of a person who is not involved in what is about to listening to. The person is listening in a passive way.
In addiction the repetition of the sound rd in the words heard and learn'd underlines this topic.
Line 2 presents the image of proofs and figures, which are showed in columns before people; this means that people are supposedly in a room during a lesson.
Also in line 3 the poet presents words and verbs of the same semantics' area : charts, diagrams, to add, to divide, to measure.
The semantic area regards math and astronomy, so a difficult subject.
The verb shown is another passive perception verb which gives a sense of passivity.
The poet tell us that people in the room applause at the astronomer's lecture, but the subject didn't, he's estranged from others, he's alienated.
Lines 4 to 8 present the speaker's response to the situation presented in Lines 1 to 4.
Speaker's reaction consist in became tired and sick, because of the complexity of the astronomer's approach to stars.
The complexity of his discourse is provided by the length of phrases, in opposition to feels of speaker which are simply and short, and refers to his simple vision of stars.
The poet mostly use figure of speech like anaphora and repetition, to underline most significant concepts, themes.
There are also the repetitions of similar sound (alliterations): heard, learn'd, heard; lectured, lecture, perfect; room, soon; mystical, moist; silent, stars.
These gives an idea of length and defines the passivity of the speaker.
The use of comma by the poet to give an end at lines , provide us a sense of pause, reflection, author wants we to reflect to things he is discussing about.
In conclusion, the text is a speaker's memory, he tells us about a university lesson, and about his reaction after astronomer's lectured.
At the end we realize that there are many ways to percept things.