When Montag gets home that first night after meeting her, he stands there, just pondering her face. The first image is that her face was very thin "like the dial of a small clock seen faintly in a dark room in the middle of the night ...all certainty and knowing what it had to tell of the night passing swiftly on toward further darknesses, but moving also toward a new sun." It is an interesting simile; a clock is steady, guiding, constantly moving forward into each new day, and cycling us onward. This could reflect the comfort that he feels from her, that he looks to her for a guide into the "further darkness"of a different life than his own, which is also "a new sun."
The second image of her face that Montag thiks of is that of "a mirror" because it took "of you and and throws back to you your own expression, your own innermost trembling thought." He feels that she, unlike anyone else he has known, has helped him to see himself for what he truly is, flaws and all. Her sensitivity to others allows them to assess where they are in life, and if it's where they want to be.
Any passage with Clarisse is filled with imagery and descriptive comparisons, and these are just two that Montag ponders.
As was mentioned in the previous post, Montag recalls Clarisse's face and compares it to a "dial of a small clock" seen faintly in the middle of the night when you get up to check the time. Montag elaborates by mentioning that the clock indicates the surrounding darkness but is simultaneously moving towards the sun. This first image of Clarisse represents the way she makes Montag realize his current circumstance. Similar to a clock, Clarisse is reliable, informative, and quiet. The darkness symbolizes the ills associated with the dystopian society while the sun represents a hopeful future. The atmosphere surrounding the image of the clock could also foreshadow Clarisse's death and beautiful afterlife.
Montag then views Clarisse as a mirror. Mirrors allow individuals to view themselves which is exactly what Clarisse enabled Montag to do. Montag shares a spiritual connection with Clarisse and is able to see his innermost fears when he looks into her face. Unlike the other citizens of the dystopian society, Clarisse takes the time to acknowledge Montag's existence and truly understand him. Montag gains insight into who he is as a person through his interaction with Clarisse.