Post the passage it will be every helpful if u need us to help
C Un forgiving due to being<span> a slave and he lost his mother and grandmother</span>
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.
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