Thoreau mostly uses imagery to illustrate time in the excerpt. The second sentence is saying that he is in the midst of time/living, and he can "detect how shallow it is," meaning that he is aware that life is short and that the end is inevitable. Thoreau also describes time as being fleeting, but ever-present.
I hope this helps!
Here's one example of a 'free verse stanza of poetry.
"Who am I?" -
Who am I, you ask?
I am a lion who comes off as a lamb.
I am an ocean with waves big enough to drown.
I am a roller coaster of emotions.
I am a hater of ignorant people, liars,
And people who use others for a gain.
I am a lost soul, a naive child.
I am one who has seen enough
That would make most people's skin crawl.
I am me, not you.
I am who I am.
Judging me is only a negative reflection on you.
So who am I, you ask?
I am me...just me.
One identification of how my poem can be considered a free verse because many people go threw many questions and common life problems. People may forget what they are and what their life meaning is. So this can be a 'free verse'.
There are two defintions of Crepusclar:
1. Something that resembles or relates to twighlight.
2. An animal active or is appearing in twilight.