The narrator describes the appearance of the snow and the distant trees of the Yukon, saying that
it was an unbroken white, save for a dark hairline that curved and twisted from around the spruce-covered island to the south.
By referring to the line of trees as a hairline, he uses a metaphor to compare them to this feature of a human head. A metaphor is a comparison of two unlike things where one is simply said to be the other.
The narrator describes the tobacco spit that freezes to the main character's facial hair as being "like glass" because, if it fell from his face, it would shatter into brittle fragments. Here, the narrator uses a simile, a comparison of two unlike things where one is said to be like the other using the words like or as. This simile seems to emphasize the man's relative weakness: how fragile he is compared to the natural world around him, which seems vast and so powerful.
The narrator uses another metaphor to describe the man's thinking about the springs under the snow,...
(The entire section contains 4 answers and 939 words.)