Mirror, Mirror on the wall...

The first stanza of "Mirror" is all about what the Mirror is and what it does. It describes how it is all knowing and all truthful, "the eye of a little god". Most of its time is spent reflecting the wall opposite it. Once in awhile it flickers with faces and darkness. The length of each line is really interesting. I feel like Plath used the lengths of the lines to emphasize the length time spent doing a particular thing or the importance of the line. "It is pink, with speckles. I have looked at it so long" is the longest line in this stanza emphasizing that the most time was spent studying the opposite wall.
The second stanza tells of the woman who seeks her reflection in the Mirror. This stanza's lines showing the length of time spent for each line. When she turns to the liars, the candles or moon, it is the second longest line possibly indicating that for a long period of time she chose to not seek or reflection in the Mirror and look for the truth elsewhere. When the Mirror reflects her back it is the shortest line of the stanza indicating that it was a short period of time. The longest line is of her going from a young girl to an old woman. This obviously took a number of years, it didn't happen over night. So that lines seems to keep going when all other lines stop.
Plath ends most of her lines with periods. Which tends to add emphasis to the lines that end in the middle of a sentences. On line 7 it breaks after "long" and then continues with "I think it is a part of my heart." That also adds emphasis to how much time is spent because it draws out the "long" until the next line. Line 10 is broken after the "woman bends over me," The eye has to move to the next line before finishing the sentence. This almost gives a movement for the woman bending. The last two lines are one very long sentences. This suggests the passage of time and how much time the woman has spent seeking the truth in the mirror day after day.