What figure of speech is used in this line from walt whitman's poem "i hear america singing"?

i hear america singing, the varied carols i hear

How to combine the two sentences in bold.

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

Describe, in your own words why you think jean-jacques rousseau decided to write confessions. your answer should be at least one hundred words.